The corrupt Lord Ambrose DArcy (Michael Gough) steals the lifes work of the poor composer Professor L. Petrie. (Herbert Lom). In an attempt to stop the printing of music with DArcys name on it, Petrie breaks into the printing office and accidentally starts a fire, leaving him severely disfigured. Years later, Petrie returns to terrorize a London opera house that is about to perform one of his stolen operas.