813

813 is a crime novel by Maurice Leblanc and was first published in 1910 (originally serialized in the French daily Le Journal).

A tycoon is found murdered and the evidence points to the world’s most notorious gentleman thief. To clear his name, he takes charge of the hunt himself, following a trail that coils around a cryptic number (813) and the initials of an invisible rival. What begins as a single case turns into a duel of wits and disguises that tests every trick in the arsenal of a master of misdirection.

The pursuit leaps from prisons and safe houses to embassies and boardrooms, exposing a conspiracy that reaches the highest levels of power. Each reveal forces a new identity, a fresh betrayal, and a tighter noose, until the mystery behind “813” locks into place with ruthless logic.

Considered one of the series’ most ambitious entries, 813 blends heist pleasures with geopolitical intrigue. Its momentum, layered puzzles, and flair for masks and doubles make it a signature showcase of clever plotting and elegant suspense.

"MR. KESSELBACH stopped short on the threshold of the sitting-room, took his secretary's arm and, in an anxious voice, whispered: "Chapman, some one has been here again."
"Surely not, sir," protested the secretary. "You have just opened the hall-door yourself; and the key never left your pocket while we were lunching in the restaurant."
"Chapman, some one has been here again," Mr. Kesselbach repeated. He pointed to a traveling-bag on the mantelpiece. "Look, I can prove it. That bag was shut. It is now open.""