Dark Maze — Thomas Adcock

Edgar Award Winner: An NYPD detective navigates a lethal labyrinth in this entry in Adcock's series of “gritty procedurals” (The New York Times Book Review).
 
The old, shabbily dressed man who walks up to Neil Hockaday in the park one morning rambles on semicoherently, though he's sharp enough to make Hockaday as a cop. He introduces himself as Picasso, makes snide comments about the policeman to an invisible companion -- and issues a vague homicidal threat just before his bus leaves.
 
Born and bred in Hell's Kitchen and now an NYPD detective, Hockaday has been exposed to plenty of strange characters. But Picasso's haunting words -- and the killings that follow -- soon have the officer searching the city for someone who considers murder his masterpiece . . .