Bailey looks out the window and catches the end of the showdown, but when Derek asks what happens she tells him anything out there isn't his concern. The clock goes from 8 hours to 13 hours. Callie is now in there, and Derek admits to her that he can't tell if one particular vessel is feeding the cord or the tumor. He'd have to make a blind cut, and if he chooses wrong the patient could stroke out and die. He decides to come back later, which causes Callie to ask if he really would finish the whole thing only to then cut the wrong vessel and have it be for nothing. Derek's fully aware of this but decides to wait anyway. It wouldn't be my choice, but I'm not a world-class neuro god, so what do I know?
Sunrise comes 21 hours into the surgery, and he has less than two inches to go. There's new drama, though, when Avery's hands start to cramp. He shakes like a leaf and Derek orders him not to move while Isaac's blood pressure starts to drop, but he can't. Instead, Lexie reaches in, talking calmly, and steadies his hands, ordering him to close his eyes and breathe. Derek then asks him if he has had anything to drink -- he's smarter than the average bear and knows that cramping means he is dehydrated, and that he's dehydrated because he didn't have any fluids, because he didn't want to take a break and give Lexie a turn holding the retractor. Avery has to admit sheepishly that it's true, and Derek calmly tells him not to apologize, but rather to step aside so his diaper-wearing sister can take over.
Hour 26, and it's time to come back to that tricky vein, to choose the red wire or the blue wire. He asks Lexie what to do and she babbles a bit, so he calls her on stalling and asks Avery, who wisely tells him he's not into gambling. He then asks Mark, but Mark tells him he won't let Derek blame him for a wrong choice for the rest of his life. I kind of think that if Derek can forgive Mark sleeping with his wife that he could eventually forgive anything, but Mark's right that it still would be a good amount of time for the blame game. Derek isn't happy that they're making him decide, and there's lots of tense waiting and looking at everyone's faces while they wait. Arizona can't watch while Callie and Cristina get a rush from it, and Hunt points out there's no logical way to make the decision.
He actually resorts to "Eenie Meenie Miney Mo" but when Lexie calls him on it, he laughs a bit deliriously and admits he knows it's a bad idea. There's a whole lot more dramatic shots of everyone's eyes and the drums reach a crescendo... then Derek's voiceover begins again. "Ask most surgeons why they became surgeons, they usually tell you the same thing. The high. The rush. The thrill of the cut. For me, it was the quiet." After a few more beats, Callie yells that he made the cut, and Mere begs Cristina to tell her if it was the right one.