A famous cyclist named Jeff (played by Kristoffer Polaha) who wants to race in the Tour de France is brought to House's clinic after collapsing during a race and being treated at the scene by medics. He is surprisingly honest about several illegal medications and techniques he applied to himself, but his sickness is not caused by any of these. House believes he is not completely honest, whilst Cameron does not cope well with Jeff's foul play.
In the course of making a diagnosis the team deduced the presence of an air-embolus. When the air-embolism was found and removed, without helping his symptoms followed by system-wide muscle weakness, Encephalitis or nerve-damage or paraneoplastic symptomatic bone cancer is differentiated, none of which is confirmed. Then and throughout most of the episode, House is convinced he is taking animal cultured Erythropoietin (short half-life EPO) which acts by binding to a specific erythropoietin receptor (EpoR) on the surface of red cell precursors in the bone marrow, stimulating them to transform into mature red blood cells. As a result the oxygen level in blood reaching the kidney rises and the amount of EPO produced naturally decreases, thus presumably causing all of Jeff's symptoms as he fails to produce red blood cells on his own (Anemia caused by acute Acquired pure red cell aplasia). However, after responding to Prednisone (an Immunosuppressive drug) treatment by losing more red blood cells to the point of requiring a transfusion, House instructs to go scan his neck, when a Thymoma is found (causing chronic PRCA and previously countered Myasthenia gravis). The team realizes that Jeff's illegal treatments have inadvertently been keeping the aplasia under control, and now that the condition has been diagnosed, he can continue his performance-enhancing Blood doping without penalty, on the grounds that it is medicinal (at least until the required Thymectomy is done and takes effect in up to 3–5 years, at which point medicinal Steroids may also be prescribed).
In the mean time, Stacy's husband Mark attends therapy at the hospital. House crashes one of the sessions and gives Mark a hard time, greatly upsetting Stacy. She has an outburst in front of a patient, to House's amusement. Later, House asks her if she hates him or loves him. When Stacy replies that she does both, she tells him that her psychiatrist told her it would get better with time. The episode ends with House breaking into the hospital's psychiatrist's office, and reading Stacy's records.