The Red Thumb Mark

A theft of diamonds occurs. The only clue is a piece of paper with a red thumb print and a few drops of blood inside an empty safe that formerly contained the diamonds. The proprietor of the business refuses to let the police fingerprint his employee’s who are also his nephews. John Thorndyke is challenged with a seemingly impossible task of proving the innocence of his client, whose thumb print matches exactly the thumb print taken from the safe.