It’s Valentine's Day at Princeton-Plainsboro and the ER is short-staffed due to a snowstorm. House encounters Foreman's latest patient, Hannah, who has sustained injuries from a car accident with her mother, Abby. House notices that despite her best efforts to act injured, Hannah is not feeling a bit of pain. House determines that Hannah has an incredibly rare condition that makes her completely insensitive to pain, and he takes a special interest in her case. He orders further testing to see if Hannah has any serious injuries from the car accident that she may not be able to feel, including an unnecessary procedure that causes Cuddy and Wilson to question his motives. Meanwhile, Abby undergoes surgery for her own injuries sustained in the car accident. Hannah refuses further examination and demands to see her mother, but House has little sympathy. She and House argue about which of their lives is worse, Hannah who is impervious to pain or House who suffers from pain constantly. When Hannah passes out and her temperature spikes, the doctors realize that Hannah is much sicker than they had thought. The team takes drastic measures in an attempt to inflict pain on Hannah to measure her pain threshold, but her condition only worsens. House adamantly pushes for a spinal nerve biopsy that could leave her paralyzed, a risky procedure in which few see the benefit, especially Cuddy and Wilson, who accuse House of pushing the test to get information that may benefit his own pain management. As Hannah's body deteriorates without her so much as flinching, House works through his own chronic pain to find out why this young woman cannot feel any pain at all.