House’s new patient, Sister Augustine (Elizabeth Mitchell) has hands red with rash. While her sister nuns suggest stigmata, House suspects contact dermatitis brought on by an allergic reaction to dish soap. He gives her an antihistamine, suggests over-the-counter cortisone cream, advising that relief will take place quickly. Unfortunately, the antihistamine leaves Sister Augustine gasping for air. House believes it is an asthma attack caused by an allergic reaction to the pill. He administers epinephrine, but soon afterwards, notices a rapid heartbeat and calls for a nurse.

Dr. Cuddy is certain that House made a mistake and maybe gave the nun a much higher dosage by mistake. Cuddy will have to notify hospital attorneys within 24 hours if House cannot find an underlying cause for the heart failure. He runs his team through possible explanations. Cameron hypothesizes that it is Churg-Strauss syndrome, a systemic vasculitis that even with treatment gives patients only five years survival. Foreman takes an easier route, merely suggesting that House messed up.

Sister Augustine goes into CT, but inside the tube she becomes frantic about a smell. The doctors cancel the test and Sister Augustine screams that Jesus is coming for her. Suddenly, she suffers convulsions. Foreman notices a rash appear on the Sister’s leg as he holds her down. He finds out that the nun tested positive for herpetic encephalitis, the result of a weakened immune system. The same symptom can be triggered by the medicine which House gave her earlier. The group tries to figure out other possible causes.

House then believes that the nun may have mixed connective tissue disease. The treatment for that disease is prednisone, which is what caused these problems in the first place. House recommends a hyperbaric oxygen chamber, but Foreman is concerned that that could make things even worse. Foreman goes to Cuddy and she becomes alarmed at the rash hyperbaric treatment. Cuddy pulls House off Sister Augustine’s case.

Cuddy meets with Cameron, Foreman and Chase to discuss potential treatments. House, meanwhile, asks Chase if Sister Augustine is hiding something. Chase suggests talking to the Mother Superior, and House pays a visit to the convent. Mother Superior discusses Augustine’s troubled past as a foster child and the woman’s self-aborted pregnancy. That does not interest House, but the tea which the convent serves does; it is figwort tea, which House claims, when mixed with even the smallest level of epinephrine, causes instant cardiac arrest: House was right all along. However, there is some allergy still lurking, which has gone untreated for so long that it has metamorphosed into a monster. House decides to introduce various allergens until one causes a reaction. Sister Augustine is placed into a cleanroom, but still goes into convulsions. The doctors are baffled: what in this sterile environment could make a person react so violently?

Sister Augustine decides that God wants to take her, so she requests to go back to the convent. House yells at her for constantly running away from her problems. Sister Augustine mentions that she has God inside her, which gives House a revelation. Examining X-rays, the doctors find a copper cross IUD inside Sister Augustine’s uterus; she is allergic to copper, which also explains the initial dermatitis (caused by some recently donated copper pots and pans she had been washing.) Surgical extraction of the IUD allows the nun's full recovery.