 A nun arrives at the clinic with what appears to be a skin rash caused by an allergy, and starts to go into anaphylactic shock in reaction to the medication Dr. House gives her. When he then gives her an injection of epinephrine, she goes into cardiac arrest, leading Dr. Cuddy to assume that House gave her an accidental overdose. Absolutely sure that he gave the patient the correct dosage, House begins a series of unorthodox treatments to uncover the truth, and also does a bit of snooping into the sister s past.