Arsène Lupine against Herlock Sholmès - S1.E3

During a reception at the home of the brilliant young Maxime Bermond, the guests learn that banker Dautrec has just purchased the priceless royal diamond. Back at home, Dautrec checks the locking systems on the doors and windows. A nun is waiting to read to him. Shortly afterwards, an alarm goes off in the house. The servant finds his master murdered.