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.

Walt and the others are shocked when Michael is brutally beaten, but only the non-English-speaking Jin and Sun know the truth behind the attack. Meanwhile Kate, Jack, Sawyer and Sayid argue about where the survivors should camp -- on the beach, where they're more likely to be seen, or in a remote inland valley where fresh water abounds.

Charlie begins a painful journey of withdrawal from drugs, surprisingly aided by Locke, whose true motive for helping Charlie is a mystery. Meanwhile, survivors struggle to find and free Jack when he's buried alive in a cave collapse, and someone might be secretly thwarting Sayid, Kate, and Boone when they enact a plan to find the source of the French transmission.

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.

Jack, Kate and Sawyer fight over possession of a newly discovered locked metal briefcase which might contain insights into Kate's mysterious past. Meanwhile, Sayid asks a reluctant Shannon to translate notes he took from the French woman. A rising tide threatens to engulf the fuselage and the entire beach encampment, and Rose and a grieving Charlie tentatively bond over Claire's baffling kidnapping.

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.

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.

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.

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.