Gilder has purchased some bills of exchange on which Arthur forged the signature of Lord Chelford to pay for his own gambling debts.

Inspector Puddler of Scotland Yard and his assistant Horatio are called in when a man is found stabbed to death and they try to solve the mystery.

Mary Wenner, who used to be secretary of Lord Chelford (and an aspirant to become his wife), joins forces with Gilder to find the treasure.

Lord Chelford, plagued by his deteriorating sanity, completely loses his grip on reality when he encounters his mother (whom he believes to be dead) in the grounds of the manor.

Lord Chelford shoots his mother and the Black Abbot, takes Leslie as a hostage and hides with her in the tunnels beneath the abbey after also killing Gilder.

Sergeant Puttler (=Inspector Puddler) initially comes to the castle as a favour to Alford, he is on vacation and wants to spend it doing some light investigative work concerning the strange goings-on around the estate.

Gilder finds out that Alford is the Black Abbot—he later confesses to it, saying that he used the costume to scare his insane and at times violent brother into staying inside the estate.

[4] The script to the film was adapted by Johannes Kai and Franz Josef Gottlieb from the Edgar Wallace novel The Black Abbot (1926).

This was the fourth script Kai (a pen name for Hanns Wiedmann) had written for a Wallace film and the plot remained relatively close to the original novel.

[4] F.J. Gottlieb had just directed The Curse of the Yellow Snake produced by competitor Artur Brauner and had previously worked on Wallace scripts for Constantin Film.