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