Izzie tries to get George to find the courage to ask Meredith out. All of the interns are in awe when a woman comes in with a record breaking tumor, but it is so far advanced that the woman's prognosis is not good. Now that Bailey knows about Meredith and Derek's affair, their jobs are in jeopardy, and she advises Meredith to end it. Meanwhile, Cristina and Burke's secret relationship is also getting more complicated...

Cristina and Meredith try to figure out if Cristina should tell Burke that she's pregnant right before Cristina faces an emergency. Alex and Izzie get closer while Meredith's mother gets too close.

Train Wreck victims come to Seattle Grace and all staff gets called in. Everyone deals with really weird cases. Except Addison and Izzie. They work with a woman who is pregnant.

The holiday season has started but not everyone is in a festive mood. This is Alex's last day in the hospital unless he passes his boards practical exam the next day, thus everyone helps him to review so that he succeeds. However, Izzie is not happy about the others helping him and Meredith has to remind her of the true spirit of the Christmas holiday. Justin is in need of a new heart. One is available but he does not want it because he does not believe Santa gave it to him as his mother said. Cristina and Burke, both handling Justin's case, have opposing views on the matter due to their different stances on religion. Despite a reconciliation with his wife, Derek isn't in a festive mood. George has a simple case of a woman who has a bleeding ulcer, he realizes that the ulcer is caused by her entourage but fails to keep them away, with the consequence that it perforates.

Derek and Addison's relationship is rocked to the core when a former friend comes to Seattle Grace and his presence promises to shake things up for a few members of the staff. Burke and Cristina's relationship is affected when one of her secrets is outted. Alex and Izzie are having similar reactions to their closet scenes during the Code Black crisis. On top of this a cocky doctor shows up to piss Derek off in all kinds of ways. A patient is suffering from constant orgasms and her condition sparks interesting conversations among the staff. George is trying to figure out how to get Meredith to see him as more than just a housemate. Another patient, that Derek is treating, is dealing with a rare disorder and needs his parents support and understanding. Burke has a patient who inspires him to talk to Meredith and Cristina about doing what they say they will. Meanwhile, Meredith learns more about her family (in fact maybe more than she may have wanted to know) through her parents.

Cristina meets Burke's parents, the interns try to get Izzie's job back, and Addison takes a day off, a surgical patient may be living her last day. Some of the interns want to know why Bailey won't talk to Izzie. Meredith tries to decide between Derek and Finn and comes to a decision somewhat. Webber finds out that Callie has been living in the hospital and he confronts her about it.

Meredith discovers that Derek has a problem sleeping while her father comes to visit the hospital. George's father is moving from one surgery to another. A patient named Heather checks into the hospital. Heather is 17 and has a nasty attitude that results from her medical condition and all the surgeries it has required her to have. Izzie has an emotional breakdown when she tries to hand over something very important to her. George's family comes to visit to celebrate his father's surgery. Cristina and Burke are playing Uncle.

Cristina and Burke continue to play Uncle until one of them gives in. Derek and Meredith are fighting over the reason for their sleepless nights. Meredith tries to talk to her father about his side of the story. There's tension between Alex and Addison. There is even more tension between Addison and Mark. Addison confides in Callie. Bailey wishes she didn't have to keep a secret from one of the interns. Callie rushes to be with George after she learns that his dad needs an emergency procedure. Izzie may have found 'some good to do' with her inheritance.

It's Halloween at Seattle Grace! There may be jokes, pranks, and/or scare tactics. Some of the women form a club based on an experience they all share. A man volunteers for what most of the doctors believe is an unnecessary surgery. One of the patients is in the hospital because they tried to carve a pumpkin in an unconventional manner.

An ambulance crash endangers the lives of the paramedics involved, as Meredith and the Chief work on-site to save them, Bailey treats a patient who refuses her help, and Ava returns for Alex and meets his other girlfriend in the process.

Meredith works furiously to save a paramedic trapped in an ambulance; Lexie holds the life of a patient in her hands; Derek must rely on a nurse to save a patient; Bailey struggles to balance her personal life with her work.

When the plumbing springs a leak, chaos breaks out at Seattle Grace as the Chief tries to put in place new teaching methods. Meanwhile, George takes his residency exam; and Derek attempts to get Meredith's roommates to move out, much to their surprise.

As preparations continue for Meredith and Derek's wedding, Izzie receives a surprise hospital visit from her handful-of-a-mother, Robbie. Meanwhile, a newly sober Thatcher visits his daughters, Meredith and Lexie, in order to make amends, and the Chief and Meredith bitterly fight over a controversial medical case.

The hospital staff is left to deal with the aftermath of George's passing. Hitting the staff hard, they all find unique ways to get through the various stages of grief. George's mom returns, faced with the difficult task of deciding what to do with his organs.

Everyone is struggling after losing one of their own and are turning to any distraction they can find. Meredith and Derek seem to be consummating their marriage anywhere and everywhere, while Cristina and Owen have been instructed to abstain from sex by Dr. Wyatt.

As Thanksgiving, Christmas and New Year's pass, Miranda gets a visit from her father, William who disapproves of her choices in life. Mark and Lexie cope with an arrival of a woman from his past. Thatcher questions the Chief's recent behavior as Meredith comes to his defense.

In the wake of the shooting at Seattle Grace-Mercy West, the doctors find themselves in a frenzy: Christina and Owen will be getting married, and others are trying to deal with the recent blood bath. Derek is arrested for speeding!

A gunman opens fire at a local college, sending mass casualties to the hospital; Arizona's return is not warmly received.

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.

Meredith struggles to come up with a new plan for Owen’s sister. Jo makes a surprising choice regarding Alex, and Andrew’s sister’s controversial research leads to a shocking discovery.

After a roller coaster car falls off the track at the county fair, the doctors at Grey Sloan tend to patients who spark memories about ghosts from their past. The series 300th episode!

Meredith Grey and the team of doctors at Grey Sloan Memorial are faced with life-or-death decisions on a daily basis. They seek comfort from one another, and, at times, more than just friendship. Together they discover that neither medicine nor relationships can be defined in black and white.

The doctors at Grey Sloan Memorial vie for a new position. Meredith is seemingly distracted and struggles to stay focused, and Maggie finds herself the keeper of a big secret while Amelia and Owen try to figure out their relationship. Meanwhile, Jo and Alex's honeymoon doesn't go exactly as planned.

As fog begins to cover Seattle, the doctors of Grey Sloan navigate through personal complications. Meredith and Alex attempt to save Gus, while Levi talks some sense into a struggling Nico.

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.

The Grey Sloan Memorial doctors grapple with the aftermath of the car crash that involved some of their own; Meredith works to save Dr. Hamilton's life. Levi is impacted from his latest loss.

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.

After a long six months, Grey Sloan Memorial has reinstated its residency program. A group of talented and striving young interns has been recruited as the attending surgeons work to rebuild the program to its former glory. Meredith, still functioning as the interim chief, sees Nick for the first time since she rejected his offer to move to Minnesota. Meanwhile, Bailey tells Richard she is not ready to return to work; Levi works up the courage to break disappointing news to Jo, and things turn awkward when Link realizes he has met one of the interns already. With Amelia and Maggie’s help, the new doctors are thrown into their first day on the job dealing with injuries from a recent tornado.

It’s Meredith’s last day at Grey Sloan Memorial and the doctors plan a goodbye surprise, while Nick confronts her about the future of their relationship. Elsewhere, the interns compete to scrub in on Maggie and Winston’s groundbreaking partial heart transplant procedure, and Richard asks Teddy an important question.

Simone's wedding day arrives as Jo and Link's relationship hits a major turning point.