813

Leblanc published 813 in 1910, and the title comes from a mysterious number that turns up next to a corpse on the first night of the case. The setup is classic Lupin. A wealthy diamond magnate is murdered in a Paris hotel. Lupin is the obvious suspect and gets arrested, but then everything turns: he ends up working with the police, then running them, then disappearing into a new identity as Monsieur Lenormand, the head of the Sûreté itself. Yes, the most famous thief in France quietly takes over the French criminal investigation department, and nobody figures it out for half the book.

The plot threads its way through forged identities, German imperial agents, family secrets, and a German emperor cameo. Leblanc was thinking big with this one. It runs almost twice the length of his earlier Lupin novels and reads more like a thriller than the tight short-story Lupin most readers know. Critics often pick 813 as his masterpiece. If you have read a couple of Lupin shorts and want the version that takes itself seriously, this is the book.