House and the Cottages check out the sample under the microscope. Actually, just the Cottages are looking at it; House is reading one of Chase the Elder's medical textbooks and letting everyone in the room know about it. Eventually, he goes to the microscope, sees some animal hairs in the insulation sample, and orders a CT scan.
Something scary's on the CT scan of Gabe's lungs, and House blames it on the attic insulation. Cameron and Chase figure out what it is, but Slow Foreman needs an explanation. House says that poor Gabe has anthrax.
Gabe's Dad is a little skeptical of the diagnosis. Chase explains that anthrax isn't just for terrorists; it's a naturally occurring bacterium that was in the insulation. Cuddy soothes the savage beast (who calls her "Lisa") by saying that she appreciates everything Air Force One has given to the hospital, and that Dr. House is the best guy they have to treat his son. In that case, Air Force One wants to know why they're dealing with "this guy," a.k.a. Chase, who doesn't appreciate the nickname. Air Force One says he checked online and found some other diseases that cause a similar skin rash. He orders Cuddy and Chase to look into every possible condition Gabe could have before they make any conclusive decisions, and says he is going to "stay on top" of them while they do it. And with that, he walks away. So much for staying on top of everyone.
Over in Gabe's room, Gabe's airway is closing. Chase, Cuddy, and Foreman run in, and Chase takes a look inside Gabe's throat, which he reports has nodules. They'll need to intubate, but Foreman can't get the tube in. He keeps trying, and Gabe stops breathing. Chase grabs a scalpel to do a tracheotomy, and has just begun the incision when Foreman gets the tube through and Gabe is breathing again. Air Force One alternates between looking angry and looking very worried.
The Cottages follow House down the hallway, discussing why Gabe's throat closed up. It wasn't an allergic reaction to the antibiotics, since they switched medicines and the throat nodules didn't go away. House wonders what "Dr. Chase" thinks, and lets Chase get a few words in before interrupting to say he meant the other Dr. Chase. You know, the one House is using to antagonize one of the only people in the world who actually likes him.
There are now two Chases in the Differential Diagnosis room. Chase the Elder doubts the anthrax diagnosis, especially since Gabe's tell-tale rash hasn't turned black. Apparently, anthrax rashes get necrosis, which is nasty. Cameron supports the Elder's theory, because she's a bitch. Chase the Younger defends his theory, saying that the rash can take as long as two weeks to turn black. Chase the Elder sips his coffee. Chase the Younger makes an angry smirking face. House hasn't had this much fun watching a fucked-up relationship play out since the last episode of GH he watched. He puts Chase the Younger's diagnosis to a vote, and it gets no support. Therefore, it's time to figure out what else Gabe could have. Chase the Elder suggests sarcoidosis. They'll go with that.