Eight strangers are invited by a mysterious unknown host to spend the night in a penthouse apartment. The eight (5 men, 3 women) are wined, dined, then greeted by their host's voice via a radio broadcast. The voice announces that before the night is over each one will be systematically murdered unless they manage to outwit their ninth guest Death. Based on the mystery novel The Invisible Host (1930) by Gwen Bristow & Bruce Manning.