David doesn't recognize anybody at his new high school, and he never will. He has prosopagnosia, a neurological disorder that prevents him from recognizing people's faces. With a few tricks and the help of a best friend, David manages to keep his disorder a secret and lead a normal life at school. When he witnesses his best friend's murder, however, David is left with a broken arm and a feeling of abject helplessness: he can't even give the police a description of the killer.
When a student confesses to the murder, David's feeling of relief is short-lived. Although individuals with prosopagnosia can't tell who people are, they can sometimes tell who people aren't, and David knows that the confessing student is not the murderer. But after David argued for so long that he doesn't know what the murderer looks like, nobody believes him when he claims the real murderer is still among them.
Now David's own life is in jeopardy unless he can catch the killer, but solving this crime won't be easy: he's no better at recognizing any potential witnesses or suspects than he was at recognizing the murderer. Still, he can't give up. He's needed help identifying people all of his life; it's finally time to return the favor, and identify for his school the face of a murderer.
