How many episodes in 4 season: 17 episodes
Entering their first year as residents, Meredith Grey, Cristina Yang, Izzie Stevens and Alex Karev now have interns of their own to mentor. The interns are welcomed by new chief resident Callie. Among the new interns are George, forced to repeat his internship after failing his exams, and Lexie Grey, Meredith's half-sister. Many new interns will be introduced in this season premiere. And they'll have their hands full when a three-car accident sends multiple casualties pouring into Seattle Grace. Some of the doctors need to deal with their new stressed out interns. A young boy brings his bleeding deer to the hospital in the hope a doctor will save her. Cristina searches for Burke. Richard resumes his post as chief of surgery. Derek and Meredith reach an impasse. Bailey wrestles with things at the hospital not turning out like she thought they would.
A patient is in the hospital because they fell asleep in a hazardous situation. A patient's home laboratory blew up in an apartment building and the victims flood the hospital. Alex investigates the cause of the incident by talking to an elderly resident of the apartment building. Jane Burke shows up to deal with what her son left behind. Lexie tries to talk to Meredith. Callie is overwhelmed by her new position while Bailey is searching for things to do.
A woman named Marcy brings in her son, Hunter, because she finds his change in behavior suspicious. A patient named Connie may lose her ability to talk unless Mark and Richard can perform a radical new surgery. George impresses the other interns at work but at home he is trying to deal with his guilt about having sex with Izzie. Meredith and Lexie work on a patient. The doctors meet a unique intern.
A face familiar to one of the year-twos shows up and dredges up issues that were never really dealt with. A teen football player needs counseling because of his father and surgery for an injury he sustained while playing the game. The girl who was the reason for the prom at Seattle Grace finds out her cancer is back and she brings her aunt Adele with her.
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. Alex receives a visit from Jane Doe/Ava/Rebecca. Meredith is having mommy issues. Callie has an announcement to make.
Cristina and Izzie are fighting for surgeries and a favor from someone. A patient comes to the ER with a dream and a condition which may prevent him from realizing it. The Chief turns to the other men in the hospital when his marriage is in more trouble. Two patients are competing to win something big. One of them convinces an intern to take their place.
Two arguing parents, who are named Jane and Don, bring their son in because he swallowed marbles, while a middle aged woman comes in wanting cosmetic surgery on her chin. A father worries about raising a child alone when the mother needs surgery.
There has been a bus crash and the patients are in the ER. Meredith and Derek's relationship gets more complicated when he dates a fellow doctor. Meredith's dad visits her at the hospital.
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.
George has a surprise visitor. Callie copes with not being an O'Malley anymore. Bailey's family is falling apart, by her husband not thinking she cares about her son and husband. Tuck goes into surgery with the whole hospital worried. Derek sorts through what kissing Rose means. Meredith discovers something that doesn't inspire hope or happiness in her. Alex treats a faith healer, and doesn't believe in her "powers".
Time, specifically six weeks, has passed but sexual angst still runs rampant in the halls of Seattle Grace. Derek and Rose have been dating. Meredith has noticed the activities of her current off-again ex-boyfriend. George and Lexie are getting used to their new apartment. The doctors are in the midst of a competition when a man arrives at the hospital after having survived an attack by a bear. Erica Hahn makes a friend.
Addison visits Seattle Grace because they need shugs that only she has. Rebecca/Ava returns with news for Alex. Meredith and Derek's clinical trial experiences one or two developments.
The clinical trial continues to make progress. The anti-McSteamy club creates new initiatives but that isn't enough to stop one woman from spending time with him. Cristina is affected by Burke's career developments.
Dr. Wyatt refuses to let Meredith give up on therapy. Alex learns something else about Rebecca. The Chief wants Erica to perform a daring surgery. Cristina continues to act strange.
This is the first hour of a 2-hour season finale. A two episode entries have been created. The 10pm EST marker will mark to beginning of the second episode. A couple undergoes surgery. Derek and Meredith clinical trial has another patient. Izzie helps Alex. McSteamy hooks up with someone.
This is the second hour of a 2-hour season finale. A two episode entries have been created. The 10pm EST marker will mark to beginning of the second episode. A couple undergoes surgery. Derek and Meredith clinical trial has another patient. Alex breaks down for the first time ever. Izzie offers a friend some help. McSteamy hooks up with someone. A new couple appears. Lexie gets something unexpectedly. George gets a second chance.
