The opportunistic owner (Yvonne Furneaux) of a champagne factory enlists the help of her husband (Anthony Perkins) in convincing her mentally unstable business partner (Maurice Ronet) to sell the rights to his famous last name. Soon a mysterious rash of murders occurs, with Ronet the prime suspect.
When his wife leaves him, a young French actor, François Combe, moves to New York to work for a television company. One evening, he meets an attractive young woman, Kay Larsi, in a bar.