Coward's Kiss. The Classic Crime Library, #13

"Ed London is the kind of private investigator you call to clean up the mess when your mistress turns up dead. But after he dumps a body in Central Park, it appears this case is still alive and kicking. Seems that the dead girl was in possession of something special that some very shady characters want back. Now Ed, along with his actress friend Maddy, will have to crack the case before he ends up dead himself.
But there's more than a murder here; there's missing jewels, Israeli intelligence, Nazi spies, and a host of double-dealing, backstabbing thieves."Coward's Kiss started life as a tie-in novel for Belmont Books, linked to the TV series Markham, starring Ray Milland. When a very young Lawrence Block turned in the book, his agent sent it instead to Knox Burger at Gold Medal, who shared the agent's enthusiasm.
Block rewrote the book, changing Roy to Ed and Markham to London, and Gold Medal published the book with the unfortunate title of Death Pulls a Doublecross. After fulfilling his assignment by writing another book for Belmont (You Could Call It Murder, Classic Crime Library #12) Block tried to write a second Ed London novel, but somehow never managed it. He did write three magazine novelettes with London, and you can find them in One Night Stands and Lost Weekends, a collection of his earliest pulp work.
The legendary Anthony Boucher gave the book a nice review in the New York Times Book Review, and if Lawrence Block had the sense to keep things, we'd reproduce it here. But he doesn't, so you'll have to take our word for it. This Classic Crime Library ebook edition of Coward's Kiss contains as a bonus the first chapter of the next book in the series, 69 Barrow Street.