Martin Harris returns home after a short absence to find that his wife doesn't know him and another man is living in his house under his name. The imposter shares all of Martin's memories, experiences, and knowledge down to the last detail. Is it conspiracy? Amnesia? An elaborate hoax or his own paranoid delusion? Part moral fable, part thriller, Unknown is a fast-paced tale of one man's desperate attempt to reclaim his existence-even at the cost of his own life.