In the late 1960s, graduate student Eddie Jessup (William Hurt) conducts mind-expanding experiments in an isolation chamber, using himself as the subject. Seven years later, he is a respected professor at Harvard Medical School. Believing he has lost his edge, Eddie decides to resume his work with sensory deprivation, this time using hallucinogens, specifically untested ones, to enhance the experience. After initial tests, he claims to have entered an alternate physical and mental state. Although unbelieving of Eddie's claims, his colleagues Arthur Rosenberg (Bob Balaban) and Mason Parrish (Charles Haid), as well as Eddie's wife, Emily (Blair Brown), are concerned for Eddie's well being. However, if Eddie's claims are true, he could do irreparable harm to himself and others around him, especially if his altered states are uncontrollable.