In Pursuit of M. Lachance (en Inglés) - JW Troemner

The case should be open and shut: a madman claiming to be a vampire hunter attacked a wealthy gentleman. Unfortunately, Inspector Etienne Durand knows the victim is no gentleman: he's the burglar Marcel Lachance, Durand's childhood crush, who broke his parole to live under a false name. Determined to send him back to prison, Durand goes undercover as Lachance's lovestruck suitor, hoping to get close enough to find evidence against him. But the more he entangles himself with Lachance, the more he realizes that the accusation of vampirism might not be so far off the mark.