"Slowly it rose from our souls like the mists from a landscape until peace and reason had returned, and we were sitting upon the grass, wiping our clammy foreheads, and looking with apprehension at each other to mark the last traces of that terrific experience which we had undergone."

Synopsis by Jim Hoy:

• MR. ROUNDHAY, vicar at Tredannick Wollas parish, Cornwall.
• MORTIMER TREGENNIS, a boarder at the vicarage.
• OWEN TREGENNIS, brother to Mortimer
• GEORGE TREGENNIS, another brother
• BRENDA TREGENNIS, a sister and secret lover of...
• DR. LEON STERNDALE, noted African explorer.
• DR. MOORE AGAR, prominent Harley Street physician who prescribed a complete rest for Holmes.
• DR. RICHARDS, local medical practitioner of Tredannick Wollas.
• MRS. PORTER, maid to the Tregennis household.
• HELSTON, a lunatic asylum where Owen and George were taken.

SUMMARY

Holmes has been working too hard. He and Watson take a cottage in Cornwall for a complete rest. They become friends with the local vicar who comes rushing in one morning to tell Holmes that the three Tregennises who lived together (Owen, George and Brenda) had been found. Brenda was dead and the two brothers were raving lunatics. Holmes investigates but reaches no conclusions.

Leon was at Plymouth, getting ready to leave for Africa when he heard the news. He returned immediately to Cornwall.

A couple days later, Mortimer is found dead in his room under the same conditions as those of his siblings. Holmes examines Mortimer’s room and scrapes some red powder from the smoke guard of the lamp. In their cottage, the dynamic duo attempt to reconstruct the experiment and they would have succumbed to the fumes if Watson had not pulled them to safety.

Leon was a secret lover of Brenda. He was married and estranged but could not obtain a divorce. Mortimer stole some devil’s foot powder from Leon and used it, hoping to kill his siblings and inherit their estates. Mortimer felt that Leon would be on his way to Africa and would not hear of the affair for years. Roundhay knew of Leon and Brenda’s love and telegraphed him at Plymouth. Leon returned and forced Mortimer to sit beside a lamp into which he poured devil’s foot powder while he, Leon, watched from outside the window with a pistol in his hand.

Holmes lets Leon return to Africa and tells Watson that if he had ever loved a woman and seen her treated in such a fashion, he might have acted as Leon did.

OTHER ADVENTURES MENTIONED
Dr. Moore Agar, “whose dramatic introduction to Holmes I may someday recount.”

DISGUISES
None.

UNUSUAL DEDUCTIONS & bits

• "I followed you."
  "I saw no on one."
  "That is what you may expect to see when I follow you."
• Sterndale obtained his sample of Radix pedis diaboli "under extraordinary circumstances in the Ubangi country."
• Official Abbreviation: DEVI
• The adventure of the devil's foot was first published in the Strand Magazine, December 1910

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