House diagnoses Mark, Stacy Warner's husband. Although the tests do not indicate a condition and Mark claims to be fine outside of stomach pain, it appears his brain is dying. House finds abdominal epilepsy, but cannot detect any memory loss. After Mark begins developing paralysis, House decides to treat him for Guillain-Barré syndrome. After confiding in Stacy that he still has feelings for her, House realizes that Mark had experienced delusions, and actually suffered from acute intermittent porphyria (AIP). With support from Stacy, but not from his team, House gives Mark a dangerous drug cocktail to confirm that he really has AIP. Cuddy decides to hire Stacy as the hospital's lawyer.