Derek insists his research fellow -- the woman who answered the phone -- picked up his phone after he forgot it. He says he came home because he and Meredith are "in trouble" not because, as Meredith suggests, he's in trouble.
Back in D.C. nine weeks earlier, we see that Renee Collier, the research fellow, earned some praise from Derek for some work she's done. He said he looked forward to working with her.
Back at the hospital in present day, Meredith dives right into work and tells Alex that Derek came home. Hunt and Amelia get flirty again and plan to finish the business they's started the night before.
Hunt's mom comes to the E.R. after having slipped and fallen in the shower and hurt herself when the glass door shattered. John, a firefighter, explains that she had been complaining of dizziness all day. Hunt tells John that he can leave, but that's when his mom clarifies that John -- who is significantly younger -- is her boyfriend. He becomes more and more outraged as he learns they've been dating nearly a year. John is 35, prompting Hunt to start questioning if John has access to her financial records and accounts. Webber takes Hunt for a walk.
Meredith checks on Danny, a teenage boy who's a big hockey fan, and suggests a surgery that could help him. Alex is worried the surgery is too risky.
Jo checks on a young woman who has been having headaches and nosebleeds and was in China a month earlier. She's worried she has SARS or the bird flu. Blood apparently starts to come out of her nose, but it goes back up without being touched. Jo says it's not a nosebleed.
Jackson is showing off a cool skin-grafting alternative he's been working on with Ben. Stephanie wants Ben's case, but Ben says there's no chance -- even turning down $50.
Back in D.C., in the past, we see that Derek was intrigued when he learned that Renee's big goal is to cure autism -- inspired by her little sister, who had it.
Hunt's mom opens up to Amelia during an MRI about how she started dating John and how genuine his feelings for her seem to be. She says she's having the time of her life.
Jo runs a camera up her patient's nostril and she and the patient both freak out when a "critter" of some kind, as Jo puts it later, peeks out. Stephanie swings by and Jo tells her the case is nothing.
Alex and Meredith's patient is getting frustrated and wants the surgery Meredith recommended.
Back in D.C., four weeks earlier, Derek found Renee frustrated after running into a wall with her autism research on lab rats, and he gave her an inspirational speech.
Hunt listens kindly while his mother talks about how kind and loving John is to her, but then he says there's something wrong with the equation and that "there's no way" John could actually love her. She tells Hunt to leave. Outside in the hall, Amelia says she thinks his mom's relationship is real. But Hunt is annoyed and tells her to stay out of it. She leaves.
Jo tries to catch the critter coming out of her patient, Andrea's, nose. She grabs it for a moment but Andrea panics and tells Jo not pull at it anymore, then hits Jo, forcing her grip to slip and the critter to crawl back up. Andrea says she doesn't want to try that again.
Bailey mocks Stephanie for trying to bribe Ben with $50 to take his case. She says she should have offered at least $175.
Alex and Meredith argue during Danny's surgery about what to do. Alex is worried Meredith's judgment is cloudy because of the Derek situation.
We see back a week earlier in D.C. and Derek called Renee at 1 a.m. because he was still looking at her research in the lab. She came to talk it over and Derek excitedly told her what he'd discovered.
Evelyn, Hunt's mom, tells John that they shouldn't be together. He tries to comfort her when she starts to scream in pain. Webber calls for help.
Hunt finds John waiting by himself in the hospital. John seems pretty genuine in telling Hunt that he's going to stay and wait until he knows that Evelyn is alright. Hunt sits down next to him, though they say nothing more to each other.
Meredith and Alex work on Danny while Webber works on Evelyn. Meredith and Alex come out to tell Danny's sister that he didn't make it. Meredith's eyes are full of tears and she can't even say anything as Danny's sister, Kathy, cries.
Back in D.C. again, we see a moment when Renee got so excited about Derek's contribution to her work that she kissed him.
Outside the hospital, Meredith tells Alex that Danny should have lived and she could've saved him if Alex hadn't brought her down with his doubt. Alex tells her to go ahead and take it out on him if she wants to, but she's really mad at Derek. They hug.
Webber comes out and tells Hunt and John that Evelyn is fine. John prepares to leave and Hunt stops him. John goes back to Evelyn's bedside and Hunt smiles as he watches his mom light up when John tells her she's beautiful.
With April's help convincing Andrea by gently telling her that the critter in her nose will eventually eat her brain, Jo is finally able to grab the thing -- which turns out to be a leech -- and yank it out. April asks Andrea if she wants to keep it, and Jo says that she'll keep it if Andrea doesn't want it.
Stephanie is annoyed when she finds out that Jo blew her whole day, which could have been spent on traumas, pulling a leech out of a woman's nose.
Hunt finds Amelia outside f the hospital and apologizes for the way he talked to her. And they sleep together.
Meredith, meanwhile, gets home and finds Derek in the kitchen. We flash back to Derek and Renee kissing, when he stops her and says he's married and doesn't want anything other than what he has with Meredith. He says he has to go right away -- leaving his keys and phone. Derek tells Meredith that she's everything, and that he loves and isn't going to stop. Meredith tells him that even though she can live without him, she doesn't want to.