Mer and Derek are cuddling on the floor on the morning after the wedding of Izzie that was meant to be theirs. Derek figured out a way to get Izzie's tumor, he says.
Izzie is walking with Alex because she doesn't want to spend their honeymoon in bed. She tells Alex she wants her to meet all her patient friends, as opposed to her doctor friends.
She comes into the room and announces, "I'm a bride!" and shows off the wedding ring. She introduces him to the cancer patients.
Owen tells Cristina that he had a good session with his shrink, and she asks him about his mom, who doesn't know that Hunt's back in the US.
He then asks George to follow him.
They meet a patient, Charlie, who obviously has heard of Hunt. Callie says she doesn't find anything functionally wrong with his leg, other than the fact that he can't walk or run. Callie says there's nothing she can do.
Charlie has a suggestion: cut it off and replace it with a prosthetic leg so he can get back to Iraq.
Callie is aghast at the suggestion, as Owen tries to defend his request.
Callie says if the leg is healthy, she is not cutting it.
Arizona asks Bailey if she's busy, and she gets all defensive. All those dying kids must be getting through to her, somehow.
Arizona wants her to scrub in, until the Chief comes in and borrows Bailey. The Chief asks her some questions about Santa, and opens the door to what appears to be top of the line nice surgical equipment.
Bailey is like a kid on Christmas day.
Mark tells Lexie his plans of getting a condo. He sort of hints that she move in with him, but she didn't take the hint or shot him down.
As she leaves, Derek chimes in and tells Mark it's too early.
Derek plans to surgically remove Izzie's hippocampus, which, as Dr. Swender points out, can damage her memory, etc. Derek, of course, gets defensive and admits that yes, it is possible that she'll lose her memory.
Suddenly, Izzie imagines herself with hair, on her bikini, on the beach, with Denny. They talk about the number of kids she'll have with Alex.
Izzie continues to mull over the choice she has to make. Alex doesn't want to make the decision, neither do Cristina and Izzie.
George asks Carhlie why he is so determined to go back to Iraq and is even willing to lose his leg. Charlie calls his Iraq family his "real family."
Dr. Swender shows Cristina the scans of a cancer patient who successfully overcame cancer with therapy, and says Izzie should be patient.
Bailey is having a go at her new toy, and she's obviously very happy. She's like a kid, making light saber noises. This is a ploy by the Chief to get Bailey to stay in general surgery.
Meredith points out to Yang that Izzie may not have enough time to whether through the therapy. Suddenly, Derek comes in and notices something weird, but quickly heads out, with Meredith following.
Meredith preps Izzie for surgery and shows a series of images in flashcards. Derek starts putting the right hemisphere of her brain to sleep and she needs to remember the images - dog, plane, house.
Izzie continues to mouth the sequence then stops. When asked, she couldn't say it. She can't identify it. Any of it. She can't say Meredith's name, either.
Derek, being stubborn, still wants to go through with the surgery. Alex has a talk with Derek outside, while Meredith closes the door and tells Izzie that she's not having the surgery.
Alex wants Derek to talk to him as a friend and not as a doctor. Alex asks Derek what he'd do if it were Meredith who had cancer.
Alex says Izzie is the one good thing that happened to him. Derek says he would ask Mer to have the surgery.
Meredith tells Izzie what happened, that she didn't know Meredith's name, or who Alex was. The tumor is sitting right at the center of everything that she was.
Izzie consults a fellow cancer patient, Allison, and tells her that she's permanently hallucinating. Allison says she had 15 surgeries until she said enough, and then the therapy worked. Now her brain tumor is gone.
There's no way Izzie will have that surgery now, right?
As for Charlie, Callie tries to talk him out of amputation as Owen watches on. Charlie yells at Callie that while he's not sure of the decision, he's sure that he's in hell right now.
The Chief announces to Arizona that Bailey just performed a first in Seattle Grace. Arizona is irked because she plans to have Bailey assist her in a peds surgery.
Arizona tells the Chief that she's going to cry. Blinking back tears, she tells him she's mad at him because he's her boss and he reminds her of her dad. She says it's bad to lure Bailey to surgery via robots, and in peds, there are no robots, only kids, which are not as fun as robots.
She vows to fight him for Bailey.
Izzie tells Alex that she decided not to have surgery. He, again, shouts at her and says it's for the best. He practically orders Izzie to have the surgery.
Derek is scolding Cristina for crossing the line, and Meredith says it's her fault. Meredith talks about her mother and that Elis was no longer herself because she lost her memory.
Derek tells her she made it personal, so she better go back to Izzie and change her mind.
Owen pulls Cristina aside and talks about her mother and his commitment to the army. He tells her that he decided to go back to Iraq.
Cristina says he doesn't have her support.
Charlie goes up to Callie and George and tries to apologize. He proceeds to talk about what the army means to him, and compares his being a solider to Callie's being a doctor as George takes it all in.
Izzie complains that Alex and she are already fighting to Allison. She assures Izzie that Alex will come around.
Meredith wants Cristina and her to explain again to Izzie her options, and confesses that she practically threatened Izzie to not get that surgery.
Cristina gets a page. Izzie is trying to revive Allison. Cristina takes over.
On the amputation of Charlie's leg, Callie wants someone to remind her why she's doing it as she holds on to a drill.
Owen tries to convince Callie that they're doing the right thing.
Operating on Allison, Dr. Swender and Cristina argue about something, and Swender gets defensive and asks her if she thought it was her fault.
She admits that sometimes the toxins that they use for therapy kill the patient. It's cancer, after all, and there is no cure.
Mark abandons subtlety and tells Lexie that he wants her to move in with him. During the conversation, it's made clear that they have different things in mind.
Mark wants to move in within the next one year and Lexie, the next 10. They end up in an awkward talk about marriage, then eventually walk away in opposite directions.
Izzie looks on as Swender breaks the news to Allison's family.
Cristina tells them that it's unlikely that she'll be able to breathe again on their own. This is the deal breaker in Izzie's mind.
George tells Izzie that she knows what to do and gives her a pep talk.
Meredith comes into Derek's office with Izzie and gives him the go signal but says she's also signing a DNR because she doesn't want to end up a vegetable supposed it doesn't go well.
As she is being wheeled to surgery, Alex reminds her that this is exactly what made her crazy, when Denny signed a DNR and she ended up cutting LVAD wires.
She says she does not want to live like this, with all the hallucinations, and she just wants to go to the other side rather than go through this.
Tearfully, they share a kiss.
Meredith invites Derek to go to city hall because she doesn't want to spend another day not married to her.
In a bench outside Seattle Grace, Cristina tells Owen that it is sometimes all pointless, because no matter how good you get, your patients are still going to die. And she tells Owen she doesn't want him to die.
Bailey comes into the room to two distraught people - Callie tells her she just cut off a healthy leg, and Swender says her only miracle case is on life support.
Bailey tells them to follow her to witness the "joy" of Arizona's patient's family. "That's why we do this," she says. "The joy."
Owen and Cristina are in his car, and they go to his mom's house. "I'm home," he says simply to his stunned mom. Mother and son hug.
Meanwhile, George signs up for the Army.
To be continued in part two, "Now or Never" ...