Forensic psychiatrist Jo Beckett is called to the scene of an aircraft to help deal with an erratic passenger. She figures out that he's got anterograde amnesia, and can't form new memories. For every cryptic clue he is able to drag up from his memory, Jo has to sift through a dozen nonsensical statements. Suddenly a string of clues arises, something to do with a deadly biological agent, a missing wife and son, and a secret partnership gone horribly wrong. In order to prevent something terrible happening in San Francisco, she will have to go deep into the life of her patient, hoping the truth emerges from the fog of his mind in time to save her city and herself.