A busty young blonde walks into the ER looking for Sloan, and Alex directs her over to where he is debriding (thanks readers!) a guy's leg after a deep-fried turkey accident. The girl walks up to him and immediately launches into a blunt introduction. Her name is Sloan Riley, her mom's name is Samantha Riley, and, "I'm pretty sure you're my dad." Lexie walks up then, blissfully unaware of the bomb that was just dropped, but Callie and Alex heard and are outright staring in disbelief.
Mark and Sloan have been moved to a conference room and are silently staring at one another, Mark clearly sizing her up. She stares back but her looks is much more vacant. Callie walks in carrying some supplies and asks if they've talked yet about a paternity test, as she's brought what they need to do one. Clearly no one has spoken a word, but I don't think it's ever not a good time for that in this kind of situation.
Someone clearly brought Lexie up to speed on the situation, and once she's in surgery with Derek and Arizona she freaks out that Sloan isn't much older than she is. Derek very sensitively says he's not surprised given how much Mark got around before he settled with Lexie. Arizona calls him mean -- I guess it wouldn't be a good idea to give him the slap he deserves given that he's got his hands in a child's brain. He gets back to the task at hand and swears, since he sees that he can't access the feeder veins, which means he can't repair the problem and can only do a temporary fix. Once the kid starts bleeding later, there will be nothing to do. Lexie asks the obvious, if this means they are sending a little boy home to die, and Arizona adds, "Happy Thanksgiving, Jacobson family."
Teddy and Hunt are waiting outside and couldn't be more awkward, as she resolutely doesn't look at him and they make small talk about the weather. He turns to her and says her name but she brushes him off, clearly embarrassed and not wanting to talk about what she said last week. An ambulance comes up and they jump to action, saving them from the conversation for a little while.
The Jacobsons are understandably confused and gutted since it had sounded like Derek would be able to help Nicholas no problem. Derek tells them that the only way to remove the cluster is through the sinus, leaving Mrs. J to ask why he can't then do that. I get that this was done for the storytelling, but all I could think at the time is that no doctor would just say, "Well, here's how you fix it," and then stop, leaving the parent to ask why he doesn't just do it, already. But he does, and she asks, and he tells her that no instruments exist that are small enough for a kid-sized nasal cavity, so she then asks who invents something like that. Derek, of course, looks thoughtful.