David Haller is a troubled young man who was diagnosed with schizophrenia as a child. Shuffled from one psychiatric institution to the next, in his early 30s, David meets and falls in love with a beautiful and troubled fellow patient named Syd. After a startling encounter with her, he must confront the shocking possibility that the voices he hears and the visions he sees may actually be real. With the help of Syd and a team of specialists who also possess unique and extraordinary gifts -- Ptonomy Wallace, Kerry Loudermilk and Cary Loudermilk -- David unlocks a deeply suppressed truth: he has been haunted his entire life by a malicious parasite of unimaginable power.