A car crash involving students going to their college graduation takes its toll on the residents in the ER, Derek's wedding gift is uniquely suited for Meredith - even if the oversight is not. Meanwhile, Denny's return has Derek and Bailey searching for the cause, and the results will change the outcome of the day.

Covering days one through 13, everyone at Seattle Grace fights to save Izzie and George's lives and then deals with the aftermath. Elsewhere, Hunt treats a double amputation, and Arizona has a teen with painful growth spurts.

Thatcher is hospitalized with liver failure, and Meredith fights anger and guilt while deciding her responsibility. Sloan treats an octogenarian who wants an implant. Izzie's interference in Hunt's cancer case may have deadly consequences.

Things are hostile on all fronts when a visit to the obstetrician results in some disturbing news for Meredith and Derek and Lexie loses it when she notices Meredith and April getting closer. Meanwhile, a car crash brings in multiple traumas and Jackson tries using his physical attributes to get ahead in the operating room, while Cristina's self-doubt carries outside of the hospital and into her house-hunting with Owen.

Derek lands the grant he needs for his clinical trial and all the attendings take him out to Joe's Bar to celebrate, but they get a surprise when they see someone they know already at the bar. Meanwhile, Meredith and Alex have to fend for themselves during the night shift with a nine-year-old patient who's experiencing post-surgical complications and his very pushy mother.

Despite Meredith's objections to the idea, a concerned Derek takes Cristina on a fishing trip in order to get away from it all, while Teddy, feeling directionless without Cristina, directs all of her efforts and compassion towards a dying patient who lacks the proper insurance to seek medical treatment.

Meredith feels left out when Derek breaks ground on his clinical trial; Bailey's new idea does not go over well with the chief; Callie irritates her new obstetrician.

Meredith, looking to prove she is Chief Resident material, learns that anything and everything can happen in an hour's time when she steps up to run the ER for a night; meanwhile, Bailey sneaks off with Eli and gets into a little mischief, and everyone is surprised when the Chief's wife, Adele, shows up as one of the ER patients.

Richard is desperate for Derek and Meredith to accept Adele into their Alzheimer's trial, but will Adele stand in her own way? Meanwhile Mark and Arizona have conflicting ideas of the kind of baby shower Callie wants, Teddy is freaked out when Henry has another health complication -- leaving them both a little exposed -- and the competitiveness amongst the residents for the Chief Resident position is amplified when Richard receives the green light for his diabetes clinical trial.

In a series first, the music that has been at the heart of the show and been beloved by fans comes to life for Grey's Anatomy: The Music Event. A cataclysmic event rattles the doctors of Seattle Grace to the core, as Callie, on the verge of an enormous life-changing moment with Arizona, envisions her hospital and friends as it has never-been-seen before. "Chasing Cars" (Snow Patrol), "How to Save a Life" (The Fray) and "The Story" (Brandi Carlile) are among the songs performed by the cast.

Everyone pulls together to help Callie and baby Sofia on their painstaking journeys to recovery in hopes of allowing mother and baby to finally meet; the sudden death of a clinical trial patient has Derek proceeding with more caution while Meredith makes a calculated and risky move; Alex treats a cranky old rich woman dying of cancer and gets an idea for a grandiose endeavor that is sure to get him the Chief Resident spot; and Teddy is pleasantly surprised by the return of a familiar face.

Owen organizes a baseball game against Seattle Presbyterian.

The doctors form two teams to operate on conjoined twins.

Derek encourages a hesitant Meredith to work with him again in neurology. When she complies, she listens as Derek is talking to a patient, who excitedly tells him about how she passed out in the middle of a big job interview. They're going to remove a cyst that's causing seizures. There is also a benign tumor that they aren't going to remove. Just as the procedure is past the opening skull stage, Derek is called to another OR where Morgan's baby is suffering from a brain bleed. He tells Lexi and Meredith to carry on. A slight bleed leads to another chunk of skull being removed. This opens up sight of the benign tumor. They decide to remove it because access is already present. Derek is incensed when he returns. It wasn't in the plan. When the patient awakes, she is unable to speak. Her parents threaten to sue. Jackson's mother, Catherine Avery, returns to Seattle Grace with a urology fellow, to replace a faulty bladder with one that Richard and Miranda have grown in the lab. During the procedure, Catherine develops an interest in Richard, becoming quite flirtatious. The fellow, Dr. Mara Keaton, was brought to be a spy for Catherine about how her son is doing. Jackson is forced to take her on a hospital tour. He is instantly suspicious of her motives and calls her on it. She admits that she is supposed to gather information on him. In turn, he advises Mara on how she can assert herself and gain his mother's respect. They try it out, defying her intent to take them to an awards banquet. The two of them trip off to find an empty on call room to get to know each other better. Richard is asked to the award banquet but turns her down at the last minute. Cristina becomes increasingly suspicious of Owen's every move. She finally corners nurse Emily, her prime suspect, and asks her point blank about sleeping with Owen. Emily says no. She uses a bit of flirting to get through long shifts. When Christina faces Owen, he admits he has been unfaithful to her. Alex has been working continuously to save Morgan's preemie. Callie watches Alex and Morgan work together and sees that Morgan is falling for him. He denies it. But when Morgan has her picture taken with him and the baby, you can see it in her body language.

While the hospital becomes the center of attention as the victim of a famous kidnapping case is brought to the hospital, the fifth years take their placement interviews. Meanwhile, Adele Webber's memory continues to deteriorate, forcing Richard to reconsider their relationship.

It's Arizona's first day back at work and Callie tries to keep things as normal as possible for her. Meanwhile, Bailey argues with Ben over wedding plans and Cristina and Owen continue to struggle with their relationship while Owen faces his first set of meetings about the plane crash.

A magician's assistant arrives at the hospital with a severe injury that has all the general surgeons involved, except for Bailey who is ignoring all of the attendings. As Cristina searches for a way to wake his father up, Ethan has a medical emergency of his own. Alex tries to avoid Jo at the hospital and a new cranial-facial specialist flirts with Arizona.

With a major storm rolling in, the hospital is chaotic. When Jason comes into the hospital in critical condition, Alex does everything he can to protect Jo. With Meredith's due date just weeks away, Derek urges her to slow down.

Following the storm, a mudslide injures first responders and citizens.

Callie and Derek collaborate on a brain mapping project.

Callie's career is on the line when she is being sued for negligence after an operation on a star athlete goes horribly wrong.

The doctors work together to operate on two sisters joined at the head; Cristina travels to Zurich where she deals with a blast from her past; Richard voices his concern over the hospital's allegiance with the Harper Avery Foundation.

Owen introduces Callie to the Veterans Hospital patients in hopes that she will help them with her robotic limb lab, Jo becomes jealous of Alex and Meredith's friendship, and Maggie continues to confide in Richard. Meanwhile, Alex and Bailey prepare to go in front of the board.

Arizona has to take care of one of Herman's patients. Everybody finds out Amelia was a drug addict and Derek lets her down. Jo has her first solo surgery. Maggie is invited to Ellis' house and Arizona decides to move in with Alex.

An earthquake leaves Maggie trapped in an elevator and threatens Meredith's streak of successful surgeries; Owen gives medical advice over the phone; Ben opens up Jackson.

Jackson learns about April's pregnancy, while Alex and the team of doctors handles a long triple-organ transplant surgery. Meredith considers dating again, and Andrew insists on not receiving special treatment after he and Maggie go public.

After a missing child forces the hospital into lockdown, Ben decides to operate on a pregnant mother without the proper surgical equipment. Miranda, as Chief, is faced with the repercussions of the event.

Alex learns a lot has changed at the hospital since he left; Jo has to make a tough decision on a case; Arizona tries to keep her distance from Eliza.

Meredith and the team are focused on helping Owen's sister after her shocking return, and Amelia faces a conflict over a patient. Meanwhile, Bailey is forced to give Grey Sloan a facelift after the fire and the doctors are introduced to a few new faces that spice things up around the hospital.

Two boys injured in a house fire are brought to Grey Sloan and firefighter Andy Herrera's skills are put to the test when one of the boys is near death.

New doctors continue to shake up the hospital in typical Grey Sloan manner. Meredith bonds with a patient while Jackson struggles with the meaning behind recent experiences; and after making a life-changing decision, Jo forms an unexpected alliance.

Seattle is hit by a huge wind storm and Grey Sloan becomes inundated with patients. Alex and Jo are stuck at home and decide to make the best of it by having a second honeymoon, while Meredith confronts Richard about getting his life back on track.

Meredith is troubled by Linc's nonchalant attitude. Once she has diagnosed Catherine, Maggie worried that Richard, Jackson and Catherine are not accepting the diagnosis. DeLuca get an advantage in the OR and Owen has some difficulties.

Maggie introduces mood rooms as an alternative approach to medicine. Alex and DeLuca butt heads over an 11-year-old patient who tries to sabotage her own surgery. Jackson and Richard deal with a gender non-binary patient. Meanwhile, Teddy has a pregnancy scare that brings Owen and Koracick to odds.

A patient at the hospital is brain dead after falling into a construction site, and her two sisters must decide whether or not to keep her alive.

Meredith faces the medical board as her future as a doctor remains uncertain, and she's forced to reckon with her past in some challenging ways. Meanwhile, the interns are put to the test as they are each vying to be the most successful on their respective cases in the absence of some of the attendings.

Following the car crash at Joe's Bar and subsequent rescue efforts led by the Station 19 firefighters, Grey Sloan doctors work through the night to save the lives of their colleagues. Meanwhile, Amelia worries about sharing her pregnancy revelation with Link. Owen and Teddy take a big step, and Bailey deals with grief over her recent loss.

Richard finds out Maggie quit Grey Sloan and is concerned about how she's handling the death of her patient who was her estranged cousin. Bailey returns to work after taking some personal time off, although Koracick doesn't make her first day as easy as she'd like. Meanwhile, Meredith thinks she might miss DeLuca, and Amelia has an update for Link on her pregnancy.

DeLuca has a seemingly incurable patient and turns to a diagnostics genius for help; Bailey checks in on Joey, a foster kid that Ben brought into Grey Sloan; Amelia is getting the results of her paternity test.

Owen and Link treat an older woman who wakes up from surgery and can't stop singing, while Teddy helps Koracick stay afloat after an estranged loved one from his past comes to the hospital looking for help. Meredith, Bailey and Maggie focus their efforts on a difficult patient with a tricky diagnosis.

Both teams tend to a tense situation with so much at stake. Meanwhile, Jo convinces Hayes to bend the rules on a case, and Maggie and Winston reconnect.

As traumas and pressure mount, Grey Sloan doctors try to find a path forward, and Richard questions his faith. Meanwhile, Jo, Link and Jackson play an unconventional drinking game.

Due to a blood shortage, Grey Sloan Memorial is setting up a voluntary donation center. Meanwhile, Nick asks Meredith for help with his patient and Winston is hung up on his relationship with his brother.

The blood shortage at Grey Sloan Memorial continues. Meanwhile, Meredith makes a risky decision regarding a patient, and Owen's actions to help his fellow veterans come to light.

Six months later. A new team of interns begins training at the hospital as familiar faces return.

On the heels of life-changing news, a thunderstorm hits Grey Sloan. The attending surgeons and interns work together to save an injured reporter and family affected by the storm. Meanwhile, a beloved author undergoes a risky surgery, and complications from the storm arise.

In the immediate aftermath of shocking events at the clinic, the hospital goes on lockdown and the Grey Sloan doctors split up to save multiple lives; Maggie lands in hot water with Winston; Jules' roommate makes a surprise appearance.

The attending surgeons fly to Boston, forcing a reunion between Nick and Meredith; Bailey gets a big surprise.