Finally. Derek. It's been a very long time since he's been in an episode! Let's jump right into it.
Derek is back, and Meredith isn't sure what to do about it. She distracts herself with work, refusing to talk about it with Alex. When Callie and Maggie find out that Derek is home, they realize this must be bad news - he's come home to apologize, which must mean he has something to apologize for. Alex asks for Meredith's advice on one of his patients. She wants to do a risky surgery, but Alex thinks it's a bad idea. When the patient demands the surgery, it looks like their decision is made for them. The patient dies on the table, devastating his older sister and caretaker. Meredith is angry, and lashes out at Alex for doubting her. Alex hugs her and tells her that she's not really mad at him - she's mad at Derek. He tells her it's okay to take it out on him, but that she needs to keep it together when she's being a surgeon.
We get to see Derek's story in Washington DC. He gets close to a research fellow who is working on hopefully figuring out a cure for autism. Derek and this woman do seem to have a connection, and after a breakthrough in her research, they share a kiss. Derek realizes that he doesn't want this - he wants Meredith. He rushes off to catch the first flight, inadvertently leaving his cellphone behind. Derek tells Meredith that he can't live without her, and he wants to work on their relationship. Meredith says that she can live without Derek. But she never wants to.