Composer Lord Ambrose D'Arcy (Michael Gough) and his backer, Harry Hunter (Edward De Souza), struggle to find a replacement for the female lead in their new opera after she quits in the wake of a gruesome murder. When a new prospect, the nubile Christine Charles (Heather Sears), disappears, Harry cautiously investigates. Meanwhile, a mysterious masked man (Herbert Lom) who is eerily familiar with the opera holds Christine captive and offers to groom her to play the part.