House tries to get some alone time on the hospital roof, but Stacy finds him and yells at him about what he said to her husband. House says that the questions were medical in nature. Stacy says she knew House would go running up to roof like a little twelve-year-old afterward. "I haven't been up here in five years," House says, which I took to mean that he hasn't been on the roof since his leg made it difficult to take the stairs to get there. It shuts Stacy up, wonderfully, and House admits that he doesn't know what's wrong with Mark. Every test for every possible diagnosis has been negative. Stacy says she never thought House wouldn't be able to figure it out. He steps up and hugs her and she cries tearlessly. He says he hasn't given up. She pulls away and asks what they do now. House says they'll wait for something to change.
House and Stacy don't have to wait long! Mark can't feel his toes. He frantically calls for a nurse. Stacy runs in, followed by House. Mark tells her that he's really scared and asks her to hold his hand. But she already is. The Magic School Bus Cam goes flying into his eye and through the nerves connecting his brain to his hand, which are all shorting out. "Time marches on," House says. "He's paralyzed."
House's latest theory is that Mark's mystery illness is not in his brain, but somewhere peripheral. His guess is Guillian-Barré syndrome, which requires a halfway decent knowledge of French to figure out how to spell. As my knowledge is considerably less than that, I spent quite a lot of time googling "Guilamba-Ray" and "Geelambaray" before I figured it out. Foreman says he already tested for it and there were no antibodies. House says that Mark could still have it and just not be producing the antibodies, which Foreman says is very unlikely. House says that the treatment for Guillian-Barré isn't "all that" dangerous, whereas doing nothing if Mark really had the disease would prove fatal. So he'd rather go with the treatment route and see what happens.
Mark is all hooked up to plasmapheresis machines as Cameron tells him the she doesn't know if his paralysis is permanent or not since "the brain is tricky." How reassuring. From the doorway, House gives Stacy a silent head-nod. Mark gets all suspicious that House wants to talk to Stacy for reasons that aren't medical, and says she might as well go, since she'll be leaving him if his paralysis is permanent anyway, just like she left House when he got the limp. Mark starts to cry, and Stacy says she's not going anywhere. Cameron tells him that his emotions are all out of whack because of his virus, and then Mark's throat closes up and he can't breathe. Cameron calls a code, saying it must be an allergic reaction to the drugs. She tries to intubate him, but House enters and says this isn't an allergic reaction, and that if Cameron just took a second to look at his vitals, she'd see that he isn't crashing at all. The code blue team file out and talk about how this is the seventh time today that Cameron called an unnecessary code and made them all have to run around. House asks Stacy if Mark has sweaty palms. She nods that he does. House orders Cameron to inject Mark with two milligrams of Ativan for his panic attack. She does, and Mark's throat immediately loosens up again. House checks out one of Mark's "Get Well Soon" cards and asks Stacy if they can talk now that her husband is too out of it to get all worked up again.