Ideas for story title please?

Okay so im making a Crime drama set in the 1940's and 50's. its sort of a nod toward clic Noir stories and films in that time. It's about a Detective named Johnny (age 28) who has the chance to prove himself when he is hired to catch an illusive gangster known as Percy "The Mercy" Thompson. Percy is the typical gangster who is interested in toying with the police and marvels fine art. Percy's location isn't much known and nobody has ever seen his face. In the story Johnny is engaged to his fiancee named Ann. Ann suddenly becomes kidnapped by Percy's goons and is therefore one of Johnny's motivations to catch him. While hunting down Percy, Johnny befriends an old flame of Percy's that might have info to catch him. Her name is Isis and she decides to accompany him. Ocionally they share some "tempting moments". Overall i'm more than halfway through the book. The book has some intense scenes, plenty of twists and turns, and some brain teasers as well. PLUS I HAVE A GRAND FINALE PLANNED OUT. But no title :( please help