Research scientist Eddie Jessup (William Hurt) believes that other states of consciousness are as real as everyday reality and may hold the key to another universe. Using sensory deprivation tank, he experiments with a hallucinatory mushroom, he finds in Mexico, and explores these altered states. As result, he starts to experience wild religious visions, such as visions of his goat-head flying through the stratosphere and consumed by a flaming crucifixes; a beautiful sequence with naked bodies being eroded by sandstorms; damned souls diving into flaming pits, etc. But soon, his mind-altering experiments get out of control and he endures experiences that make madness seem a blessing. The situation becomes even worse as an unexpected link of events causes him to regress genetically. Other cast members include: Blair Brown (Emily Jessup), Bob Balaban (Arthur Rosenberg), Charles Haid (Mason Parrish), and Drew Barrymore as Hurt's daughter (Margaret Jessup) in her film debute. Eddie's magical and horrific journey is paced like a rollercoaster ride. It has inspired many sci-fi films that followed, and even a song. It's an ultimate, visually striking and breathtaking picture with great performances and mind-blowing special effects of the time, one of the best science fiction tales ever put to film, featuring a number of Academy Award Nominations.