A psychiatric doctor is driven insane plagued by nightmarish visions of Coffin Joe's subterranean world of bizarre horror. Under analysis, it's discovered that he has a pathological fear that Joe has sexual designs on his beautiful wife. Unable to cure him, his fellow doctors enlist the services of José Mojica Marins, the creator of Coffin Joe, in an attempt to convince the patient that Joe does not exist. But all is not how it might first appear.