Stripped of everything, the 48 survivors scavenge what they can from the plane for their survival. Some panic. Some pin their hopes on rescue. A few find inner strength they never knew they had-like Kate who, with no medical training, suddenly finds herself suturing the doctor's wounds. The band of friends, family, enemies and strangers must work together against the cruel weather and harsh terrain. But the intense howls of mysterious creatures stalking the jungle fill them all with fear. Fortunately, thanks to the calm leadership of quick-thinking Jack and level-headed Kate, they have hope. But even heroes have secrets, as the survivors will come to learn.

Having escaped the "creature" and retrieved the plane transceiver, a group of the survivors travel to higher ground so they can transmit a signal. En route, they receive a mysterious transmission and encounter another of the island's inhabitants. Meanwhile, back at camp, Jack tends to a wounded man who reveals a secret about Kate.

Jack and Hurley discover an alarming secret about Kate, as the marshal's life hangs in the balance and he suffers a lot of pain. Meanwhile Kate, Charlie, Sawyer, Sayid, Boone and Shannon ponder the mysteries they have begun to uncover and worry that telling the other survivors will cause panic. They decide to lie for the time being. Also, Locke's befriending of Walt disturbs Michael, but Walt is more concerned in finding his dog. Lastly, Kate flashes back to when she was arrested by the marshal in Australia.

The survivors are jolted awake in the middle of the night when wild island beasts (which are wild boars) invade the beach encampment. Kate and Michael join the mysterious Locke on a hunt for food -- and a shocking secret about Locke is revealed. On the hunt for food someone is injured. Meanwhile, some survivors are horrified by Jack's plan for the dead bodies still scattered among the wreckage -- he wants to burn them. Jack sees someone that's not there, and we find out that one of the survivors was not able to walk but now he can.

Jack is nearly delirious from lack of sleep and struggles to overcome the haunting events that brought him to Australia and, subsequently, to the island. Meanwhile, Boone gets caught in a treacherous riptide trying to save a woman who went out swimming. A pregnant Claire's health takes a bad turn from lack of fluids, and a thief may have stolen the last bottles of water. Also, Jack flashes back at 12 years old, to find himself on the playground in an altercation with a bully.

Shannon's inhaler runs out and Boone believes Sawyer has the remaining three in his stash. When Sawyer refuses to give them up, Jack and Sayid resort to torturing Sawyer until he agrees to reveal the location of the inhalers. In flashback we hear Sawyer's story...

Claire has a horribly realistic nightmare about her new baby being harmed or kidnapped. Flashbacks reveal Claire's backstory. Hurley is shocked and confused when he discovers that another plane crash survivor, does not appear on the flight manifest.

Survivors wonder why Charlie and Claire have been abducted - and by whom - and a search party ventures into the treacherous jungle to look for the pair. Suspicions focus on Ethan Rom, who, it was recently discovered, was not a passenger on the doomed flight. Jack battles inner demons relating to his father, while Boone and Locke discover another island mystery.

Violence ensues and a mysterious island beast makes a re-appearance when Michael and Locke clash over Walt's upbringing. Meanwhile, Charlie is tempted to read the missing Claire's diary, and Sayid enlists Shannon to help decipher the French woman's map.

After the missing Claire returns with no recollection of what has happened since before she boarded the doomed Oceanic flight 815, Jack and Locke formulate a plan of defense against her kidnapper, who threatens to kill off the other survivors one by one unless Claire is returned to him. Meanwhile, the disappointment Charlie feels when Claire does not remember him triggers recollections of a woman he had let down in the past.

Kate and Sawyer divulge dark secrets to each other while tracking a renegade boar that Sawyer swears is purposely harassing him. Hurley and Sayid worry that Charlie is losing it after facing a brush with death and killing Ethan with 6 bullets to the chest. A shocking prior connection between Sawyer and Jack is revealed in a flashback...

When the raft the survivors have been building mysteriously burns down, Michael is convinced that Jin is responsible for the sabotage, which only serves to escalate their rivalry. Meanwhile, Sun stuns her fellow survivors with a surprising revelation, and Boone gives Sayid a warning about his step-sister Shannon. Lastly, more details of Jin and Sun's troubled marriage are revealed through flashbacks.

When Hurley becomes obsessed with the French woman and heads into the jungle to find her, Jack, Sayid and Charlie have no choice but to follow. Hurley flashes back to the hugely life-altering experience he had before boarding the plane.

Locke thinks he's being sent a sign on how to get the hatch open, and he and Boone venture inland. Jack is reluctant to offer assistance when Sawyer begins to experience excruciating headaches and needs glasses.

While trying to make contact with the outside world from a plane discovered in the jungle tree canopy, Boone Carlyle is critically injured when the plane suddenly shifts and crashes to the ground, so Jack Shephard desperately tries to save his life. The flashbacks in this episode revolve around Jack's marriage to a former patient, Sarah.

After another funeral, tempers rise as the survivors' suspicions of each other grow, and an unlikely survivor vows revenge. The events that landed Sayid on Flight 815 play out as he engages Locke in a psychological game of cat and mouse to uncover the truth about the mishap that claimed Boone's life.

Jack suspects foul play when Michael becomes violently ill while building the raft. The suspects include Sawyer and Kate, who compete for the last seat on the raft and do anything possible to prevent each other from getting it. Meanwhile, a secret from Kate's past is revealed to the other survivors on the island.

The French woman shocks the survivors by showing up to the camp with a dire warning about "the Others". Meanwhile, Michael and Jin ready the raft for sailing. In flashbacks, we see the survivors final moments before they boarded their fateful flight.

The castaways on the raft run into unexpected trouble. Meanwhile, the remaining islanders attempt to blow open the hatch. Flashbacks continue to show the survivor's final moments before boarding their fateful flight.

A visitor to the encampment could be a threat to Claire's son.

Jack, Locke and Kate explore the mysterious hatch but Jack decides to wait before going down into the hatch. Kate and Locke aren't so patient. When Shannon chases after Vincent the dog, she encounters a familiar face in the jungle.

With the abduction of Walt fresh on their minds, their raft destroyed, and Jin missing, Michael and Sawyer fight for their lives in the middle of nowhere in the ocean and discover a new predator in the roiling sea. Meanwhile on land, Locke must descend into the hatch when Kate goes missing inside. Also, Jack isn't too far behind Locke as he decides to go into the hatch as well later on. Lastly, flashbacks reveal more of Michael's troubled relationship with ex-lover Susan and their baby son Walt as they fight over custody for Walt and Michael must let go.

Jack, Locke and Kate learn more secrets about the hatch. Meanwhile, after being beaten and taken captive, Sawyer, Michael and Jin wonder if their captors are fellow survivors or the dreaded "Others." Flashbacks reveals more of Locke's past as well as the introduction of Helen who shakes things up even more with her revealing personality and past.

Hurley struggles with an assigned task inside the hatch as he flashbacks to disturbing memories in his life before the crash. Meanwhile, Sawyer, Michael and Jin learn the identities of their captors on the island. Claire uncovers a startling piece of information about the fate of the raft.

Michael sets off into the jungle by himself determined to find Walt, but discovers that he is not alone. Meanwhile, Sawyer and Jin are ordered by their captors to take them to their camp, and Sun frantically searches for her missing wedding ring. In flashbacks this episode reveals more of Jin's life before ending up on the island.

Sawyer's wound becomes life threatening as he, Michael and Jin make their way through the interior of the island with the tail section survivors.

The harrowing first 48 days in the lives of the tail section survivors are revealed. Flashbacks reveal the point of view of Ana-Lucia, Mr. Eko, Bernard and Libby and other survivors as they landed on the other side of the island on the beach. As the days progress danger hits their camp as well when "The Others" start taking people against their will...

Violence erupts when Ana Lucia and her group stumble upon Sayid and the other castaways on the island. Kate and Jack care for Sawyer when Mr. Eko brings him back to the camp himself. Flashbacks reveal Ana Lucia's troubled life.

As Kate’s backstory continues, her original crime is revealed. She thinks something is haunting her through Sawyer. Locke and Eko make an interesting discovery about the film, and Michael has a mysterious encounter with the computer.

This episode will shed more light on why Eko took a mysterious 40-day vow of silence, and possibly information on his stick. Also, Claire begins to lose faith in Charlie after Eko begins to question him about the Virgin Mary statue, and Kate gives the recovering Sawyer a much-needed haircut.

Jack, Locke and Sawyer follow after a determined Michael after he heads into the jungle toward the dreaded "Others" in search of Walt. Meanwhile, Sun has a surprising reaction to Jin's desire to join the search party, and Hurley and Charlie commiserate over the age-old conundrum of "what women want."

When Charlie's vividly surreal dreams lead him to believe Claire's baby, Aaron, is in danger, Locke suspects Charlie may be using again. Meanwhile, Sawyer encourages Hurley to act on his attraction to Libby.

Some of the island survivors fear that "The Others" may have returned when Sun is greatly injured during a failed kidnapping attempt at her plant garden. Also, the trust barrier becomes very thin between Locke and Jack in terms of locking up the guns and being kept safe. Meanwhile, Sawyer is an amused but highly interested bystander when tension escalates between Jack, Locke, Kate and Ana Lucia. Lastly, flashbacks reveal more of Sawyer's con artist past.

After Sun is attacked, some of the survivors begin to think that one of the "other survivors" might be one of "The Others." When French woman Danielle Rousseau leads Sayid to a mysterious captive in the jungle, he becomes determined to find out if he is one of "The Others". Meanwhile, Sawyer discovers Hurley’s potentially devastating breach of the survivors’ trust and blackmails him into helping track an elusive island creature that won’t leave Sawyer alone.

A mysterious illness that baby Aaron suddenly contracts sends a desperate Claire, Kate and French woman Danielle to return to the same area where Claire was initially kidnapped. It is there where she believes she can find a cure for Aaron's illness. In the meantime, Jack and Locke are doing their best to keep their prisoner a secret from the rest of the survivors on the island.

Sun comes to a realization and struggles on whether to tell Jin about the situation. Meanwhile, with no success from Jack or Sayid, Ana-Lucia is called in by Locke to interrogate the new prisoner Henry Gale to get more information out of him about the balloon that he and his wife supposedly landed on the island with.

When the hatch suddenly takes on a life of its own, Locke is forced to enlist the help of an unlikely ally to control the matter. Meanwhile, Ana Lucia, Sayid and Charlie go off into the jungle to find out the truth about Henry Gale and see if there really is balloon craft out there in the jungle that carried him and his wife to the island.

Libby lends a helping hand to Hurley to support him when he begins to think the island is having a strange effect on him. Hurley begins to see Dave on the island, who was his friend in the mental institution Hurley was in. Also, Locke's sense of purpose is shaken when the prisoner gives him new information about the hatch.

Rose is surprisingly and vehemently opposed to Bernard's plan to create an S.O.S. signal; romantic sparks are rekindled between Jack and Kate when they trek into the jungle to propose a "trade" with "The Others"; and Locke begins to question his faith in the island.

After finding an exhausted Michael in the forest, Jack and Kate bring him back to the main camp. When he finally wakes up, Michael has some new details about "The Others." Also, a lovestruck Hurley plans a date for Libby.

Mr. Eko has dreams about his brother leading him somewhere. He seeks Locke's help in finding a secret location, the "question mark." Meanwhile, Jack and the other survivors grapple with the horrific situation in the hatch.

A determined Michael convinces Jack and several castaways to help him rescue Walt from "The Others." With Jack away, Locke is left in charge of the hatch and must decide if he should believe Henry and not push the button, risking everyone's safety. Meanwhile, the events that happened to Michael after he left are finally revealed. Meanwhile, Charlie struggles with Eko's decision to discontinue building the church.

After discovering something odd just offshore, Jack and Sayid come up with a plan to confront "The Others" and hopefully get Walt back. Meanwhile, Eko and Locke come to blows as Locke makes a potentially cataclysmic decision regarding the "button" and the hatch. Lastly, Desmond returns and he sheds some more light on his experience on the island in the three years prior to when Locke came down into that hatch.

After discovering something odd just offshore, Jack and Sayid come up with a plan to confront "The Others" and hopefully get Walt back. Meanwhile, Eko and Locke come to blows as Locke makes a potentially cataclysmic decision regarding the "button" and the hatch.

Jack, Kate, and Sawyer are prisoners of the mysterious "Others." After their captors drug them and take blood samples, they are held in separate areas. The camp leaders--Ben, Mr. Friendly and a new woman, Juliet--try to make the castaways adjust to their new circumstances. Flashbacks reveal more about Jack's past with his father and his wife Sarah.

Sun and Jin's lives are put in danger when Sayid tries to locate Jack and the other missing castaways. Sayid also creates a plan in order to get the attention of the "Others" on the beach. Meanwhile, Henry gives Jack an offer that is very tempting in exchange for his cooperation. Lastly, Kate and Sawyer must adjust to harsh conditions that are being forced upon them by "The Others."

Locke, Eko and Desmond are found scattered about the island after the implosion of the hatch. Locke receives a message from the Island asking him to fix the situation he caused. Hurley returns to the beach camp to report the imprisonment of Kate, Jack and Sawyer by the Others. Desmond has been fundamentally altered by the implosion, giving him a mysterious new power.

The Others prevent Sawyer and Kate from escaping, leaving Sawyer perplexed by the extent of the measures taken to keep them imprisoned. Jack is asked to use his medical training to save the life of one of the Others. At the beach, Desmond's strange behavior attracts attention. He begins to construct a mysterious device.

A delirious Eko wrestles with past demons; some of the castaways go to the Pearl station to find a computer they can use to locate Jack, Kate and Sawyer; Jack does not know who to trust when two of the Others are at odds with each other.

Jack makes a decision regarding Ben's offer. Sawyer's life is placed in danger when Pickett decides to make good on his threat. Locke discovers a hidden message that may help unlock the island's secrets. Kate recalls memories from the past, which caused her to make an important choice.

Jack has the Others in a desperate situation as he holds Ben's life in his hands. Meanwhile, Kate and Sawyer try to escape from their captors. Flashbacks reveal Juliet's past as a medical researcher in Miami.

After Desmond rescues Claire from drowning, Charlie gets Hurley to help him find out why Desmond has seemed able to predict the future. Desmond recalls exactly what took place in the moments after he turns the key, where he experienced a strange vision of his life prior to his Army days.

As Kate and Sawyer journey back to the main island with Karl, who is exhibiting effects of the brainwashing video, they argue over whether to go back and save Jack. On Hydra island, as Juliet's fate rests in his hands and a power struggle within the Others ensues, Jack recollects the time he spent in Phuket, Thailand and his relationship with Achara, a mysterious tattoo artist.

Kate is still struggling over their decision to leave Jack in the hands of the Others as she and Sawyer return to their camp. Meanwhile, Hurley finds an old van in the jungle and attempts to use it to help a fellow survivor in need of faith and hope. Flashbacks reveal more of Hurley's tumultuous past with the numbers curse.

On their mission to rescue Jack, Kate, Sayid, and Locke stumble upon a mysterious structure surrounded by farm animals and meet its strange inhabitant. Back at the camp, in order to reclaim his belongings, Sawyer plays in a ping-pong competition.

Claire has an idea to send a message to the outside world. Charlie, however, is resistant to the idea, and Desmond tries to sabotage the plan. As Claire tries to get the truth behind their actions out of the pair, she remembers traumatic events from her past. Meanwhile, the rescue party encounters a dangerous obstacle.

When Kate and Locke arrive at the Others' camp, Ben promises to tell Locke the island's secrets as long as he stops his destructive plan, and Kate's reunion with Jack doesn't go very well when she learns that the Others have offered him a deal. More of Locke's troubled past is revealed.

As the truth about Sun's kidnapping by "the Others" comes to her attention, Hurley becomes suspicious of Sawyer's attempt to reveal the mystery behind two fellow survivors, Nikki and Paulo. Through series of flashbacks we will discover what Nikki and Paulo were doing before the crash and how they survived 65 days on the island.

Kate and Juliet are stranded in the jungle after Kate learns that there is a traitor in the survivor's midst. Meanwhile, Sawyer's poor attitude and selfish ways towards the beach community may earn him a vote of banishment if he doesn't have a change of heart.

The celebration of Jack's return is cut short when he arrives at the beach with an Other, Juliet, whose flashbacks pick up from where they left off, showing us how she got onto the island and became an other. Meanwhile, Claire is threatened by a strange illness.

Desmond convinces Hurley, Jin, and Charlie to follow him on a trek through the jungle after he receives a series of visions. Flashbacks reveal the time that Desmond spent with a cloister of monks. Meanwhile, a despondent Kate turns to Sawyer for companionship after seeing Jack and Juliet together.

Sun allows Juliet to examine her when she learns that all of "The Others" pregnant woman died before they gave birth on the island. Meanwhile, Desmond and an unlikely nemesis collaborate to save a new island inhabitant's life.

After abandoning the Others, Locke takes Sawyer on a trek through the jungle to help him eliminate a common enemy. Meanwhile, back at the beach, the parachutist Naomi has crucial information about flight 815.

Ben unwillingly divulges information to Locke about the island, taking him on a journey to various locations including strange monuments and the mysterious Jacob. Flashbacks will show us the origins of DHARMA and the history of the island, including 'the purge.'

While Jack devises a plan to do away with "The Others" once and for all, Sayid uncovers a flaw in "The Others'" system that could lead to everyone's rescue. But it requires Charlie to take on a dangerous task that may make Desmond's premonition come true.

The castaways are preparing for an invasion by the slightly less mysterious Others, while Charlie and Desmond find more than they were looking for in the underwater "Looking Glass Hatch".

The castaways are preparing for an invasion by the slightly less mysterious Others, while Charlie and Desmond find more than they were looking for in the underwater "Looking Glass Hatch".

The survivors feel that rescue is close at hand, but they don't know whether or not to believe Charlie's final message that the people claiming to liberate them are not who they seem to be. As unlikely alliances are formed, those they thought could be trusted may turn against them, as the enemy of their enemy becomes their friend.

The survivors begin to question the intentions of their supposed rescuers when four strangers arrive on the island.

Locke's hostage may be the key to getting off the island, so Sayid and Kate go in search of their fellow castaway in an attempt to negotiate a peaceful deal.

Kate needs to get information out of the hostages, but it may jeopardize her standing with Locke -- as well as with Sawyer. Meanwhile in the future Kate's Court hearings take place.

Sayid and Desmond hit a bit of turbulence on the way to the freighter, which causes Desmond to experience some unexpected side effects.

Juliet receives an unwelcome visit from someone from her past and is given orders to track down Charlotte and Faraday in order to stop them from completing their mission -- by any means necessary. Meanwhile, Ben offers Locke an enticing deal.

Juliet is forced to reveal some startling news to Jin when Sun threatens to move to Locke's camp. Meanwhile, Sayid and Desmond begin to get an idea of the freighter's crew when they meet the ship's captain.

Sayid confronts Ben's spy on the freighter, and Ben urges daughter Alex to flee Locke's camp in order to survive an impending attack.

Jack tries to discover the identity of a body that has washed ashore. Meanwhile, Locke's camp is attacked by Ben's adversaries.

Kate and Juliet must learn to work together when Jack's health is seriously compromised, and something goes wrong as Sawyer, Claire, Aaron and Miles continue their trek away from Locke's camp and back to the beach

Locke finds out where Jacob's cabin is. Life on the freighter becomes dangerous.

Sayid goes back to the island to bring the rest of the people to the freighter. Ben, Locke, and Hurley go to another Dharma station in order to "move the island".

The face-off between the survivors and the freighter people continues, and the Oceanic Six find themselves closer to rescue.

As the face-off between the survivors and the freighter people continues, the Oceanic Six find themselves closer to rescue.

Kate discovers that someone knows the secret of Aaron's true parental lineage. Meanwhile, the dramatic shifts through time are placing the lives of the remaining island survivors in extreme peril.

A parallel universe, in which the crash never happened, is revealed as an aftermath of the bomb's detonation. Meanwhile, Sawyer blames Jack for the loss of Juliet and the true identity of the monster is revealed.

Jack, Sawyer, Kate, Miles and Hurley, struggling to save Sayid, face an ancient secret. Meanwhile, a fake Lock exits the chamber to everyone's awe.

Kate finds herself on the run, while Jack is tasked with something that could put a friend's life at risk.

Locke goes in search of help to further his cause. Kate finds herself on the run, while Jack is tasked with something that could put a friend's life at risk.

Hurley must convince Jack to accompany him on an unspecified mission, and Jin stumbles across an old friend.

Sayid is faced with a difficult decision, and Claire sends a warning to the temple inhabitants.

Ben deals with the consequences of an uncovered lie.

Locke tasks Sawyer with a mission.

Richard Alpert faces a difficult choice.

Sun and Jin desperately continue their search for one another, and Locke confronts his enemy.

Desmond wakes up to discover he's back on the island.

Hurley worries about what the group should do next and Locke is curious about the new arrival in his camp.

Alliances are forged and broken as the Locke and Jack camps merge.

After the remaining survivors are reunited, Sawyer and Jack hatch a plan to divert the Man in Black's attention and leave the island without him on Widmore's submarine, but disastrous consequences await them. In the flash sideways, Jack investigates the cause of Locke's paralysis and offers treatment.

The motives of John Locke are finally explained.

While Locke devises a new strategy, Jack's group searches for Desmond.

Jack, the new protector of the island, meets with Locke and they go past the bamboo field with Desmond to visit the heart of the island. The Man in Black's final fate is determined, and one survivor must make the ultimate sacrifice to save the island. Meanwhile, in another life, the ones who might have been the survivors gather for a final time.

The Man in Black's final fate is determined, and one survivor must make the ultimate sacrifice to save the island. Meanwhile, in another life, the ones who might have been the survivors gather for a final time.

Claire has an idea to send a message to the outside world. Charlie, however, is resistant to the idea, and Desmond tries to sabotage the plan. As Claire tries to get the truth behind their actions out of the pair, she remembers traumatic events from her past. Meanwhile, the rescue party encounters a dangerous obstacle.

A mysterious illness that baby Aaron suddenly contracts sends a desperate Claire, Kate and French woman Danielle to return to the same area where Claire was initially kidnapped. It is there where she believes she can find a cure for Aaron's illness. In the meantime, Jack and Locke are doing their best to keep their prisoner a secret from the rest of the survivors on the island.

Claire has a horribly realistic nightmare about her new baby being harmed or kidnapped. Flashbacks reveal Claire's backstory. Hurley is shocked and confused when he discovers that another plane crash survivor, does not appear on the flight manifest.

After the missing Claire returns with no recollection of what has happened since before she boarded the doomed Oceanic flight 815, Jack and Locke formulate a plan of defense against her kidnapper, who threatens to kill off the other survivors one by one unless Claire is returned to him. Meanwhile, the disappointment Charlie feels when Claire does not remember him triggers recollections of a woman he had let down in the past.

Kate finds herself on the run, while Jack is tasked with something that could put a friend's life at risk.

Hurley must convince Jack to accompany him on an unspecified mission, and Jin stumbles across an old friend.

Sayid is faced with a difficult decision, and Claire sends a warning to the temple inhabitants.

While trying to make contact with the outside world from a plane discovered in the jungle tree canopy, Boone Carlyle is critically injured when the plane suddenly shifts and crashes to the ground, so Jack Shephard desperately tries to save his life. The flashbacks in this episode revolve around Jack's marriage to a former patient, Sarah.

Alliances are forged and broken as the Locke and Jack camps merge.

Locke tasks Sawyer with a mission.