Charlie has a neurological disorder in which strong emotions, especially joy, make him faint. He lives with his brother. Working as librarian gives him a quiet environment, but then Francesca enters the library and his life.

Charlie suffers from cataplexy, a symptom of narcolepsy that causes sudden bouts of paralysis whenever he experiences strong emotions -- in particular, joy. He develops a variety of techniques to deny himself too much pleasure and happiness, but they're put to the ultimate test when he falls in love.