Klaus Kinski stars in this horrifying and gruesome thriller, as a crazed maniac who is obsessed with trapping young women and then slowly torturing them to death. Karl Guenther (Kinski) is a conscientious landlord who looks out for his young and attractive tenants. Jessica, a rising young soap star, Harriet, a sensuous and vivacious secretary and Sophie, an accomplished pianist who enjoys wild fantasy sex with her boyfriend - all live in Karl's well kept apartments. The only discord is the "tap, tap, tap" sound at night from the crawlspace above their rooms. Karl tells them its rats, but in reality it is Karl spying on them. One by one his tenants become victims - each one put to a gruesome test. Only one tenant remains to disclose the diabolical Karl and she enters the crawlspace - she is alone with a madman capable of anything.