Shockwaves rock Seattle Grace this season. Will Alex reveal Meredith's hand in the tampering of a major medical study? Loyalties will be tested, relationships will be strained and everyone's future will hang in the balance.
Meredith loses her job; April tries to fill the role of chief resident.
Zola's adoption counselor worries about Meredith and Derek's relationship; Cristina makes a difficult decision.
The chief makes a decision that shocks everyone at Seattle Grace; Owen and Cristina attempt to find normalcy; April struggles in her new role; the 5th-year residents receive their first solo surgery assignments.
A stampede at a comic book convention leads to an influx of colorful characters in the ER; Mark continues to make life difficult for Jackson; Ben returns and realizes Bailey has moved on.
The residents try to impress Jackson's mother, Catherine Avery, when she comes to Seattle Grace to perform a groundbreaking surgery; Alex and Arizona encounter a familiar face in the ER; Bailey makes a choice about her love life.
Through Lexie, Meredith tries to get Derek interested in a patient's rare brain tumor; Callie ends up being annoyed when Mark and Arizona finally form a friendship; Teddy and Alex look into alternative surgeries for a superficial patient.
Owen organizes a baseball game against Seattle Presbyterian; Lexie is unable to control her emotions when she sees Mark with a new woman; Alex fights for Zola; Richard talks to Meredith and Bailey about their feud.
George O'Malley's mother comes to Seattle Grace for help after another hospital botches her surgery; a medical miracle inspires the residents; Jackson's suspicions about Mark and Lexie interfere with work.
Teddy is called away on another case, as Henry is brought in for emergency surgery; Derek and Meredith finally receive news about Zola; a patient experiences complications after surgery.
The eldest daughter of a family involved in a car crash must make a difficult decision; Teddy asks Cristina to help with an O.R. patient; Lexie works with Mark's new girlfriend during a surgery.
The doctors form two teams to operate on conjoined twins; Bailey uses Meredith as a buffer between her and Ben; Alex learns a tough lesson; Teddy asks Cristina about Henry's surgery.
Richard's 10,000th surgery is a liver transplant for two sisters; Derek and Lexie take on a case that had been declared inoperable; Teddy and Cristina try to swipe a case from Alex and Dr. McQueen; Meredith tries to choose a specialty.
Meredith dreams of what her life would have been.
Callie surprises Arizona with a romantic evening.
Amelia arrives at Seattle Grace to beg Derek to help with the gliosarcoma case; Cristina and Owen have heated arguments during marriage counseling.
As Adele's condition deteriorates, Richard considers making a change.
Derek asks Meredith to work with him in neuro again; Catherine Avery comes back to Seattle Grace and takes an interest in Richard; Cristina becomes increasingly suspicious of Owen; Morgan may be falling for Alex.
A lion breaks loose in Seattle, leaving a couple's lives and relationship at risk. Lexie overhears Mark's discussion about moving in with Julia; Teddy begins to take steps towards coming to terms with Henry's death. Callie grills Arizona on her past lovers and Alex requests to be taken off Morgan's preemie case when she becomes too dependent on him. Meanwhile, Meredith tries to be a support for Cristina as the tension between her and Owen hits a boiling point.
A devastated Cristina presses Owen to confess the intimate details of his affair; Mark takes his new authority very seriously when he steps in as chief for the day and butts heads with Richard over a patient's liver transplant; and Callie deems Meredith ready for the boards, while the rest of the residents continue to stress about the exam.
The doctors work on a Jane Doe, who turns out to be the subject of a case that gained national interest. Cristina proves to be the highest in demand as the residents begin their interviews for post-residency positions at prospective hospitals and Richard is faced with an unsettling realization when he visits Adele at Rose Ridge.
After eight years of practice, the residents head to San Francisco for their oral boards; sparks fly between Catherine and Richard when they bump into each other at the hotel; Bailey intervenes after Owen and Teddy get into a heated argument about their young car crash patient; and Mark tries to recruit Lexie for one of his cases. Meanwhile, Alex feels guilty for being away from the hospital when Tommy's health begins to fail.
The residents agonize over their oral boards, reliving every answer they gave during their exams; Arizona's close childhood friend comes to Seattle Grace for medical help; the doctors work on a patient who is missing one third of his skull; and Julia asks Mark to start a family with her. Meanwhile Catherine tells Richard that one of his residents has failed.
The residents determine their future as they make their final decisions regarding post residency positions; Mark admits to Derek that he is torn between his love for Lexie and the fact that Julia can give him everything he's ever wanted; Ben plans something extra special for Bailey, but she is preoccupied with her work; and Arizona encourages her childhood friend, Nick, to have surgery. Meanwhile a couple on their third honeymoon come to the hospital complaining of mysterious symptoms.
Faced with a life threatening situation, the doctors must fight to stay alive while trying to save the lives of their peers; Bailey and Ben make a decision regarding their relationship; and Teddy is presented with a tempting offer. Meanwhile, Richard plans a special dinner for the residents.