524 "Now or Never" » All the Shades of Grey

George stuns everyone with the news that he's joined the Army to be a trauma surgeon. Miranda and Callie plan an intervention for later that day to stop him from reporting for duty the next morning. Arizona doesn't understand why they have to stop him, saying it's "awesome," that he's joined up. Callie can't believe Arizona won't back her up and asks, "Who are you?"

Arizona demands to know why Miranda isn't jumping for joy at the news she's been awarded a prestigious pediatrics fellowship. Miranda explains it's a big decision: If she accepts the job, along with the extra hours of training, her husband will divorce her.

A severe trauma case comes in: A man who jumped in front of a bus to save a woman he didn't even know. The team works on him frantically, debating whether they can save his arm. His skull is bashed in, so he can't speak and he has no I.D., so they dub him, "John Doe." The woman whom he saved tells Meredith how she was mean to him, just before he saved her life, but now she's decided he's her Prince Charming, and refuses to leave his side.

During surgery on John Doe, Owen wonders how George will do in Iraq. "You think he can handle it?" he asks and Callie says, "No, I don't." But Derek says, "I think he's going to surprise us all," and Mark predicts, "He's coming home in a body bag." Meredith asks them all to "shut the hell up."

Alex starts writing down vital infromation on notes for Izzie, notes like, "Derek got the whole tumor out." And "Your memory sucks." He repeatedly quizzes her on details like what time she got up, but she can't remember any of it. Cristina tells him that Izzie needs to rest, but Alex believes she needs to exercise her memory, "before it all turns to mush." Cristina threatens to ban Alex from her bedside if he keeps badgering her and he insists that Izzie's future depends on him.

Cristina wants to know if Meredith is happy, if the therapy worked. "Are you better now?" she asks. Meredith confesses she's getting married today and Cristina hands her something new (a pack of Post-its), something borrowed (a pen), both blue. After lamenting about Izzie's condition, Meredith says, "It's important to tell the people you love how much you love them while they can hear you." She smiles and says, "I love you Cristina Yang." "You have changed," says Cristina, who goes to tell Owen that she loves him and that she "can't breathe without you." Owen tells her, "We can do this. Just meet me halfway. All you have to do is say yes."

Arizona tells Callie why she thinks George enlisting is a good thing: "My brother died because there weren't enough doctors over there. So for my money, George O'Malley is a patriot. So yeah, the word I use is awesome. That's who I am." Callie stops her from leaving the room and apologizes.

Alex keeps drilling a fatigued and confused Izzie until she tells him to back off. "You made me promise you that you wouldn't live like this," he shouts. "So now what am I supposed to do? Smother you with a pillow?"

Miranda asks Richard if there's still a spot available in general surgery. He can't believe she's asking to come back when he's finally given her his approval to join pediatrics. "Tucker gave me an ultimatum: My fellowship or our marriage," she explains, saying she's going to leave him. But she has to turn down the fellowship because now she's going to be a single mom.

Meredith panics because there isn't time to get married, between watching Izzie, George's intervention, and all their surgeries. Derek tells her they can get married another day, but she replies, "There is no other day. Every day is like this. Every day is a crisis. I love you and I want to marry you today, but there is no time."

He asks her if she has a piece of paper and suggests they write their vows right then. She hands him a blue Post-it. "What do we want to promise each other?" "That you'll love me even when you hate me." "No running," Derek suggests. "We'll take care of each other even when we're old and smelly and senile. And if I get Alzheimer's and forget you," she adds and he says he'll remind her who he is every day. He writes it all on down and asks her to sign. "This is our wedding? A Post-it?" she asks, but she signs it and Derek says, "Now I kiss the bride."

Izzie unloads on Cristina about how Alex threatened to smother her with a pillow and they both realize that she's got her memory back.

Cristina finds Owen and tells him, "Yes."

Callie and Miranda are stunned to learn that George has already left the hospital: Richard told him to take the day off and spend it with his mother.

John Doe tries to communicate with Meredith. He spells out "007" in her palm. She realizes with a shock who he is: It's George!

Alex gets the news about Izzie's memory having returned and joyfully hugs her, saying, "You're back," but she collapses in his arms. Alex tries to revive her but Cristina reminds him that she'd signed a DNR. "Alex it's not what she wants," she says, but he keeps working on her. "Screw the DNR," Richard shouts and they all try to bring her back.

We see Izzie, in the prom dress she wore the day Denny died, get into the elevator. The door opens and George is waiting for her in uniform.