House's new patient, Sister Augustine, has hands red with boils. While her fellow nuns suspect stigmata, House suspects dermatitis brought on by an allergic reaction to dish soap. He gives her an antihistamine, suggests over-the-counter cortisone cream, and sends the good Sister on her way. 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 notices a rapid heartbeat and calls for a nurse.
Dr. Cuddy is certain that House made a mistake and possibly gave the nun the wrong dosage. Cuddy will have to notify hospital attorneys within 24 hours if House can't find an underlying cause for the heart failure. He runs his team through possible explanations. Cameron wonders if it is a disease that gives patients only five years to live with treatment. Foreman goes the easier route -- House messed up.
Sister Augustine goes into MRI, 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's holding her down. He finds out that the nun tested positive for herpetic encephalitis which causes a weakened immune system. This same symptom can be triggered by the medicine House gave her earlier. The group tries to figure out other possible causes.
Mixed connective tissue disease? The treatment for that disease is prednisone, which caused these problems in the first place. House recommends a radical treatment - a hyperbaric oxygen chamber. Foreman is concerned that will 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. The Mother Superior discusses Augustine's troubled past as a foster child and the woman's self-aborted pregnancy. That doesn't interest House, but the tasty tea that the convent serves does.
It is figwort tea, which when mixed with even the smallest level of epinephrine causes instant cardiac arrest. House was correct all along. However, there is some allergy still lurking that has gone untreated for so long that it has manifested into a monster. House decides to introduce various allergens until one causes a reaction. Sister Augustine is placed into a hypoallergenic room 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.