Bailey teams with Seattle Grace's new pediatric surgeon, Dr. Arizona Robbins, to save the life of a young patient near and dear to her heart, as the admittance of a death row inmate at the hospital stirs anger in Derek and further erodes Meredith and Cristina's friendship; meanwhile, Callie and Sloan work as a team to fight their respective attractions to Sadie and Lexie, and Izzie tells Alex that she's seeing Denny.

A gas tanker explodes on a Seattle highway, causing multiple injuries, including paramedic Matthew. Meredith and Jo help a frantic mother whose child is suffering from a mysterious illness. Owen bonds with a young boy whose parents are in critical condition. Meanwhile true colors are revealed when Alex is forced to work with Jo's boyfriend on an ailing patient.

Information about Amelia's past emerges and causes problems for her at the hospital.

A patient's condition sparks a conversation between Richard and Maggie about Alzheimer's disease; April and Jackson struggle to return to their normal lives and Arizona is faced with the reality that Callie is moving on. Meanwhile, Meredith reveals her biggest fears about Derek.

A familiar face returns to Grey Sloan, throwing many of the doctors for a loop. With Catherine putting on the pressure, Bailey has to make a decision about Alex while a tough ER case makes Amelia’s bad day even worse.

Patients flood the hospital after gunfire goes off at a parade; a blast from the past throws Maggie off her game on the same day that Meredith tries to talk to her about dating Deluca; Owen and Amelia get some potentially life-altering news.

Ties are strained as Andrew and Carina confront an unforgiving family history. Meanwhile, Teddy and Owen work together on a married couple who is expecting, and Amelia attends a conference for alternative pain relief.

Meredith, Richard and Alex must deal with the consequences after Bailey fires them from Grey Sloan for insurance fraud. After disappearing in the fog, Jackson helps a man in a dangerous situation, as his relationship with Maggie comes to a new crossroad. Meanwhile, Tom gets new responsibilities at the hospital that throw the doctors for a loop.

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.

A wealthy inventor arrives at Grey Sloan and asks Koracick for help, while Meredith struggles to save a woman with diabetes who has been rationing her insulin. Jo and Link fight to save a young man who fell onto train tracks, and Jackson and Vic's relationship hits a snag.

Owen faces a medical diagnosis that challenges more than he imagined. Meanwhile, Koracick begins to go stir crazy; and Maggie gets a not-so-subtle glimpse into Winston's background.

The Grey Sloan doctors spring into action after an explosion rocks Seattle, with the incoming trauma hitting close to home. Owen experiences PTSD after he hears the explosion, while his sister Megan enlists help from Winston and Hayes in confidence. In Minnesota, Meredith and Amelia meet up with a familiar face who assists in their study.

The crossover starts on Station 19 S05E05 Things We Lost in the Fire (I).

Addison makes a special appearance at Grey Sloan to welcome Bailey’s new OB/GYN trainees. Maggie’s lung transplant is derailed, and Nick bonds with Lucas — before the day takes a shocking turn.