Dossier 113 (Aka The Blackmailers)

Introducing M. Lecoq – widely believed to be the inspiration for Sherlock Holmes
Monsieur Lecoq of the French Sûreté is called to investigate a bank robbery in one of the world's first detective novels, widely credited as the inspiration for Sherlock Holmes.
The book begins with a bank robbery with Fauvel's bank losing 350000 francs. Only two people in the bank had a key and the combination to the safe and they were Fauvel himself and his chief cashier, Prosper Bertomy. The case looks black against the cashier – the only one to know about the money being put into the safe from the strong room.
As things look blacker and blacker for prosper amidst double-dealing, blackmail, and murder Monsieur Lecoq of the French Sûreté steps in to prove the young man's innocence in the face of incriminating evidence and unravel the truth behind a seemingly impossible crime.

Émile Gaboriau (1832–1873) was a French writer, novelist, journalist, and a pioneer of detective fiction. Gaboriau was born in the small town of Saujon, Charente-Maritime. He was the son of Charles Gabriel Gaboriau, a public official and his mother was Marguerite Stéphanie Gaboriau. Gaboriau became a secretary to Paul Féval, and after publishing some novels and miscellaneous writings, found his real gift in L'Affaire Lerouge He is probably best known for his stories involving a young police officer named Monsieur Lecoq, whose character was based on a real-life thief turned police officer, Eugène François Vidocq (1775–1857).