The Black Abbot

The ruins of Fossoway Abbey are rumored to conceal the legendary Chelford treasure. Harry Chelford's hereditary disease threatens to drive him insane at any time, adding urgency to the search. The mystery centers on whether the treasure exists and whether Harry's condition will shape the outcome.

Leslie Gine, Harry's fiancée, finds herself more attracted to Dick Alford, Harry's cousin and the steward at Chelford Manor. This affection complicates the loyalties surrounding the Chelford fortune. The romantic tension weaves into the broader intrigue.

Arthur Gine, a London lawyer, is being blackmailed by his chief clerk Gilder over forged bills of exchange using Lord Chelford's signature. The ruse is meant to cover Arthur's gambling debts and secure money for himself. The threat tightens the knot around the Chelford family.

A mysterious figure known as the Black Abbot is seen moving about in the old ruin and is believed to guard the treasure. A man is found stabbed to death, triggering Inspector Puddler of Scotland Yard and his assistant Horatio to investigate. The suspect list includes the butler Fortuna, a former prisoner of Dartmoor.

Mary Wenner, formerly secretary to Lord Chelford and a rival in love, teams up with Gilder to locate the treasure. They uncover scroll cases containing maps of the abbey as clues. Their enthusiasm is cut short when they are driven off by the Black Abbot.

Wenner and Gilder return to the abbey only to find that the maps have disappeared. The loss heightens the sense of danger surrounding the treasure and the mysterious guardian. The pursuit of the treasure becomes more perilous.

Wenner is shot and killed, apparently at the hands of Arthur Gine. The murder escalates the fatal web of loyalties and betrayals surrounding the Chelford family. Arthur's act seals his own peril as the confrontation unfolds.

Arthur Gine is killed in a confrontation with Gilder, removing one thread of the blackmail plot. The interwoven schemes begin to collide as the family and their associates head toward a deadly climax. The losses mount around the Chelford fortune.

Leslie Gine calls off her engagement to Lord Chelford, cutting a personal stake in the unfolding crisis. The decision underscores the unraveling of trust within the Chelford circle. The impending danger to the treasure intensifies the characters' motives.

Harry Chelford's grip on reality deteriorates as he encounters a mother he believes to be dead in the manor grounds. He shoots his mother and the Black Abbot, then takes Leslie hostage and flees into the tunnels beneath the abbey. The line between madness and murder becomes the central tension of the finale.

It is revealed there have been two Black Abbots all along: Fortuna, the butler acting for Gilder, and Alford, aligned with the family doctor Loxon to care for the insane Lady Chelford. The deception explains the guardianship of the treasure and the various impostures around the abbey.

A police shoot-out culminates in Lord Chelford being killed by a cave-in. Among the stones fall chests that actually contain the legendary treasure. The mystery resolves in tragedy as the treasure is recovered but the family loses its heir.