An accident brings a busload of high school students into the hospital. The driver, Marcus, happens to be someone Miranda knew -- and still has a crush on -- from high school. George is amazed to see her stitch up the man's arm himself. Erica diagnoses a slight heart condition and tells Miranda that if she weren't busy flirting, she could have made the diagnosis herself. George asks if they were high school sweethearts and, as Miranda is filling out Marcus's insurance forms, she admits that she was only his tutor. Richard instructs Miranda to let Marcus fill out his own paperwork and just then Marcus goes into cardiac arrest.
Cristina is jubilant that she's back on rotation with Erica in cardiology, but can't find a way to impress her. Callie tells her to back off or she'll blow her chance.
The hospital staff relives its own high school cliques in tending to the students: Lexie admits she never knew how to relate to unpopular teens -- like the patient with the pencil stuck in his eye -- since she was prom queen and class valedictorian. Izzie advises her not to broadcast that fact. Derek is able to remove the pencil but the boy, Danny, goes into a coma. His best friend waits to hear if he'll be okay and Derek doesn't know how to tell her he's not going to ever wake up.
Both Izzie and George confide in Meredith about their rotten sex life and how they can't talk to each other anymore. Callie is pleased to hear that Izzie and George aren't even getting along. Word is soon all over the hospital, to Izzie's dismay. She demands her key back from George since he's apparently been telling everyone that they broke up. George pleads ignorance, saying he only talked to Meredith.
Derek finally has no choice but to tell the friend that Danny is never waking up. Izzie tries to console the girl, but she says Izzie couldn't understand, since she's one of "them." Izzie assures her she wasn't a prom queen, and with Lexie listening, tells the student that she was "the girl in cheap clothes from the trailer park who got pregnant." She assures her that she'll get through it and she knows what it's like to lose a best friend.
George is waiting for Izzie when she gets home. He says he only talked to Meredith because he can't talk to her anymore. They agree they miss being each other's best friend.
Cristina skips the cardio surgery on Marcus, which she desperately wants to be in on, because she doesn't want to be labeled as a brown noser. She's excited when Erica finally pages her, even if it's to chew her out for not bringing her all the scans she needed.
A nurse tells Derek she's touched he took Danny's condition so hard. "You don't even know who I am," she says and he remembers that she's the nurse in the OR who talked about how there are just as many cliques in the hospital as there were in high school. Derek is intrigued as he watches her walk away.
Callie consoles an injured cheerleader that her life is not over, just because she won't be captain of the squad anymore. She says that because of her own demotion, she gets to go back to what she loves, which is surgery.
After his surgery, Miranda is moved when Marcus thanks her for always taking care of him... and then asks if she finished his paperwork. George, who overheard, tells her that Marcus deserves a tongue-lashing for the way he's treated her and Miranda just walks away. She ends up taking her anger out on Derek, because "guys like him" don't understand "girls like her," saying that even though she's a successful surgeon, she might as well still be the awkward teenager in a band uniform who tutored the track star but never got asked to the prom. Derek tells her he was a scrawny little band geek himself and that he would have been honored to take a girl like her to homecoming.
Meredith is dismayed to see Derek on a date with Sydney. Then Thatcher shows up drunk at the ER. Alex had first tried to find Lexie but turned to Meredith when she blew him off. Thatcher apologizes to Meredith for what he said the last time he saw her and that no longer blames her for Susan's death. He admits his drinking is out of control because today was Susan's birthday. While Meredith patches him up, he tells her he how proud he is of her.
Lexie is angry with Alex for letting Meredith treat Thatcher, because he had promised not to tell her about their father's drinking. Alex tells Lexie he doesn't "do secrets" and that he was cleaning up after his own drunk of a father since he was 7.
Meredith tells Lexie how tough it must have been for her and Thatcher today, it being Susan's birthday, and that he was actually rather charming. She advises Lexie to keep a better eye on her father and Lexie bitterly tells her, "Every day is my mother's birthday. He's a drunk," she says, adding how he always goes on about how proud he is of Lexie, when he's not calling her an "ungrateful bitch." Meredith is devastated to find out everything her father said was a lie.
Derek finds the nurse -- after finding out her name is Rose -- and tells her he should have known her name. She agrees, especially since she's worked on 36 of his surgeries!
Sydney dumps Derek: She doesn't think he's ready to date! So he joins Meredith at the bar and they leave together, but he catches Rose's eye as they walk out.