Eccentric millionaire Frederick Loren (Vincent Price) invites five people to a "party" he is throwing for his fourth wife, Annabelle (Carol Ohmart), in an allegedly haunted house he has rented, promising to give them each $10,000 with the stipulation that they must stay the entire night in the house after the doors are locked at midnight. The five guests are test pilot Lance Schroeder (Richard Long (actor)), newspaper columnist Ruth Bridges (Julie Mitchum), psychiatrist Dr. David Trent (Alan Marshal (actor)) who specializes in hysteria, Nora Manning (Carolyn Craig), who works for one of Loren's companies, and the house's owner Watson Pritchard (Elisha Cook Jr.). Pritchard disapproves of Loren's use of the house for his "party," making it unclear how Loren acquired access to the house in the first place.