Mark and Callie arrive at the hospital and keep talking about the pregnancy while walking down the hall. They're playing rather fast and loose with this secret, just chatting away in normal voices out in the open, but fortunately there isn't anyone who awkwardly overhears and therefore thankfully is no excruciating storyline wherein Lexie finds out about this from a third party. Callie tells Mark that even though Arizona said she's in, Callie's not moving back in until she's really sure Arizona won't bolt. I... it's just... clearly, no one is going to call Callie on this one-sided, revisionist crap wherein she's just the innocent victim so I need to just stop commenting on it and I will instead just pray that this ends soon and I don't pull all of my hair out in the meantime. From here on out, we'll just go with whatever they are trying to feed us about their relationship and that's that. Lexie bounds up then and tells Mark she wants to make him dinner at his place, and after she leaves Callie assures him that she's letting him off the hook and that he could just be the kid's "cool uncle." He doesn't need reminding of what happened the last time an unexpected Sloan baby turned up, but she mentions it anyway. Despite all that, he forcefully assures her that he wants to be the kid's dad. Callie rightfully points out that he's going to have to tell Lexie, and soon, if that's the case.
Mere finds Derek at the surgery board and accuses him of sneaking out of the house that morning because he was starting his clinical trial and felt guilty that she wasn't on it. He tells her she's right, but that he didn't feel guilty nor did he sneak out. So... what was she right about, then? I guess the obvious, that his trial started that day. Meredith is even more offended by the situation when she realizes Alex won the job of assisting on this trial. Derek just tells her that Alex made the best pitch for the job. If she were a cartoon, steam would be coming out of both of her ears right now but Derek just kisses her and heads off while she yells at them.
Derek's next patient is Daniel, and Daniel's wife is the always-awesome Rose from Lost. He's having a good day and is able to joke with her and the doctors, and Rose is anxious to know, if he gets the medicine, how soon will it help his slipping in and out of reality? Derek doesn't make any promises and reminds her there's a two-year follow-up process but she's understandably a bit desperate and asks if this might reverse his condition completely, as it did in some animal testing. Alex decides to field this answer and while he's not unkind, he's quite direct as he reminds her that human reactions could be different. Derek comes in to play Good Cop, and reminds her that right now the most important thing is that they stop the disease progressing; he then tells them that Alex will be able to answer any more questions they have leading up to the procedure. Poor Rose is trying to stay cheerful but this is obviously one heavy burden she's been shouldering.