Clearly she caved, because the Chief then walks inside and asks Derek if he cancelled all his surgeries to work on a spinal cord tumor. It's a dumb question, and Derek doesn't say anything, so Richard walks further in and reminds Derek that the risk of infection increases the longer he keeps Isaac open, plus this is costing thousands of dollars for him to do nothing. At least he pretends to care about the patient first, though you know that was just his single smart move of the day because I'm sure the thousands of dollars are foremost in his mind. He demands that Derek close up and leave the OR, and while he hasn't said a word the whole time, after a moment Derek quietly agrees. The Chief makes a point of stopping the surgical clock.
Once Isaac wakes, Derek tells him there was no way to do the surgery without risking his life, and that he won't cut the cord while Isaac is still walking but they can reassess in a few months. Isaac is just as zen as ever, and tells Derek he knows that he worked hard and is tired, and they'll just try again tomorrow. Derek tries to tell him know but Isaac just smiles at him and says, "Go home, sleep on it, we'll talk more tomorrow."
At home that night, Meredith tells Derek that she doesn't understand, and he tries to convince her that there isn't anything to understand -- he stared for 10 hours. He tries to change the subject and asks about her day, so she lets him know that she slept, ate a box of cereal, left messages for Izzie and tried and again failed to read Anna Karenina. He recognizes that she's trying to get back to talking about the tumor and she agrees, so he turns and seems really excited to start to explain it all to her. They go back and forth a bit and he tells her there was no path for him to cut, but when she asks why he has no answer. After thinking a moment, he jumps up, pulls the bed from the wall and then around so that Meredith is facing the space where her headboard just was, and pulls out a Sharpie to start drawing the spine and tumor on the wall. She points out that now he's lost his mind and she's really not wrong -- seriously, who does that, even if they are some surgical (or any other type of profession) god? But she smiles at him as he talks it out and draws on the wall, right underneath their framed marriage post-it.
It's now morning, which we can tell by the birds chirping, the pale light in the window, and the now multicolored and labeled drawing on the wall. Derek is going over how anything they propose could go horribly wrong, so Meredith finally suggests cutting the draining veins to expose the arteries. He tells her that they are thin and could burst, leaving him a quadrapalegic, so he might as well cut the cord. Meredith reminds him that he didn't cut the cord even though Isaac said he could, which, does he seriously need reminding of that? Why not try if the worst outcome is the one he was prepared for in the first place? She goes on that Derek stood there for 10 hours, knowing the Chief would stop him, and there must have been a reason. Sheer panic is not one she mentions, and so Derek thinks it over. There is quite an impressive amount of thinking (and pondering, and musing) in this episode.