When a man claiming to be from outer space is brought into the Manhattan Psychiatric Institute, the mental ward seems to be just the place for him. However, the patient is unlike anyone Dr Gene Brewer has met before. Clever, inscrutable and utterly charismatic, prot has no traceable background, though he insists that he is from the planet K-PAX, a world without wars, government or religion, and where every being co-exists in harmony. After he sets a departure date to return home, the other patients clamour to join prot on his journey. And soon even his psychiatrist finds himself wondering.