The Thanksgiving holiday is more difficult for the interns and residents than any of them is willing to admit, as Izzie plans a big dinner at Meredith's -- but it remains to be seen who among the invited guests will actually show up. Meanwhile, George endures the O'Malley tradition of hunting turkeys with his less-than-sophisticated family, and Meredith treats a patient who's been in a vegetative state for 16 years.
Meredith and Cristina just want to drown their sorrows in alcohol, but are called to duty when the bartender collapses.
Alex discovers that the serious injuries a family has recieved in a car accident is only the start of their problems.
Meredith's mother's condition is made public when she is brought to the hospital for surgery. Everyone learns about Cristina's pregnancy when she has a medical scare.
Cristina proves the adage true that doctors make the worst patients. Ellis keeps the staff on their toes.
A woman's ultra-religious father does not want her to have an operation that could save her life.
While Meredith is awaiting Derek's decision about his relationships, a train crash with several severely injured people provides some distraction.
Cristina, Meredith and Izzie care for a man who purports to be pregnant, a case which has the hospital staff intrigued. Derek treats a wheelchair-bound girl, while George gains an understanding with the husband of one of his patients.
A visit to Seattle Grace by friends of Derek and Addison shakes up their relationship. George contends with a patient who didn't want to survive their five story fall. An old man has to come to terms with the prognosis on his wife.
A pregnant woman carrying multiple babies tries to come to term despite medical problems. Meredith has a one night stand, but her partner shows up at the hospital with a subsequent medical snafu. Meanwhile, a male patient tries to drive a good friend out of his life to avoid embarrassment over his tough medical hurdles, and Alex continues to be a source of irritation for Izzie.
Cristina clashes with a prison inmate patient who has injured herself to avoid solitary confinement. Izzie continues to fume at Alex, and is also the recipient of a rough tutorial from Dr Addison. Meanwhile, the prematurely-born quintuplets are continually monitored by the intern staff.
The gang helps Alex pass his boards practical exam so that he can stay on at the hospital, an act of generosity that irks Izzie. Meanwhile, a little boy needs a new heart, but turns down the one that is ready for him.
Izzie finds that she has chemistry with a patient who is awaiting a heart transplant and George treats a teenage hermaphrodite who is frustrated by pre-pubescence.
Meredith and Cristina lie to one another about the status of their relationships and George is given the task of discharging an elderly patient who is no longer sick, but refuses to leave the hospital.
The doctors are on their own when the nurses go on strike at the hospital. Alex, Cristina and Izzie decide to go to work, while Alex stays in solidarity with the nurses.
Meredith's fears that she is in for a bad day are realized when a medical case arrives at Seattle Grace that threatens the lives of everyone in the O.R.
The code-black situation in the OR worsens.
Someone from Derek and Addison’s past arrives in Seattle and shakes things up. Meanwhile, Burke learns about Christina’s secret and, after a visit with her mother, Meredith looks into more of her family’s dirty laundry.
George's outburst lets everyone know he slept with Meredith when he thought she had already told people.
Derek and Addison accept that their relationship is what it is. When Bailey tells Christina to watch her baby, her day turns bad.
The doctors become superstitious after a series of coincidences.
Meredith's father surprises her with a visit and her sister.
Meredith accepts a date with Finn, Izzie misses George, Alex betrays Addison, Burke performs surgery on his musical hero.
The hospital deals with a family involved in a car accident, and the surgeon who caused it. Derek's emotions get the best of him, and he takes it out on Meredith. Callie feels isolated from Izzie and Meredith. Denny wants to leave the hospital. Cristina falls asleep during sex with Burke.
Meredith gets paired with Callie, and asks for her medical opinion about Finn's diagnosis of her dog. A pregnant girl becomes brain dead due to a restaurant shooting, and her parents want to keep her alive to save the baby. Addison is convinced that something is going on between Derek and Meredith and the tension gets the best of her. Izzie, desperate to put Denny first in line for a heart, takes drastic measures.
The first hour of part two of the season finale. Burke has been shot, and his life is in Derek's hands. Izzie has taken drastic measures to save Denny's life which puts all her friends' jobs in jeopardy. Chief Webber's wife brings their niece into the hospital who had complications with her ovarian cancer during the prom.
Richard questions each of the interns about who was responsible for what happened with Denny. Callie confronts George about his feelings for her. Meredith and Derek have to put their dog to sleep. The interns plan a prom for Richard's sick niece. Izzie gives Denny an answer to his proposal.