House meets Jeff and his manager and is his typical rude self to them both. He asks Jeff if he's using erythropoietin, which shall henceforth be known as "EPO," the performance-enhancing drug du jour. Jeff denies it, saying that EPO is dangerous, and House smugly remarks to Cuddy that this is, in fact, the same old movie about the lying druggie athlete. Then Jeff admits to "blood doping." "Plot twist!" Cuddy sing-songs in what might be the best line delivery this show has ever had, which is saying a lot. Manager says she's sure Jeff's admission will be kept confidential, and House threatens that it won't, but no one really believes him. Cuddy buries her face in her hand. Jeff gasps that he hasn't done any blood doping lately, since the race he was in was a charity ride, not a competition. That explains why some bikers chose to ride on their mountain bikes, I guess. House wants to know what Jeff does when he's preparing for a real race, and Jeff admits to sleeping in a hyperbaric chamber and injecting electrolytes, anabolic herbal supplements, amphetamines, and diuretics into his blood. Whatever happened to Gatorade? House snarks that he can't imagine why Jeff isn't feeling well, and Jeff says he knows that doping has risks, but that he does what he thinks he has to do to "kick ass" at his job. "Don't you?" he asks House. House can't respond, since his mouth is full of painkillers.
We go to the whiteboard, where House tells the Cottages that this case is a little different: instead of giving them a whole bunch of symptoms and trying to figure out the cause, this time he has a whole bunch of causes and only one symptom. Foreman thinks the extra red blood cells Jeff's been injecting into his blood stream to boost his endurance have thickened his blood and caused a clot, leading to his respiratory distress. Cameron thinks the hyperbaric chamber naps have over-oxygenated Jeff's blood, damaging his cells and causing a pulmonary edema. Chase thinks the yomhimbine in Jeff's supplements caused nerve paralysis, specifically, the nerves that control Jeff's lungs. All of their theories have already been disproved by various tests. There's something wrong with Jeff that they can't see. Foreman is the first to figure out what House is saying: Jeff shoots up several times a day. Just one slip could put an air bubble into Jeff's veins, causing his respiratory problems. The Cottages are off to check Jeff's veins. House is confident that he's solved the mystery.