Jeffers, who penned one of the more soporific recent Sherlock Holmes spinoffs (The Adventure of the Stalwart Companions), does somewhat better in this evocation of jazz/gangster Manhattan in the Thirties--as narrated (in the medium-boiled-shamus manner) by Harry McNeil, a p.i. whose office is above the Onyx Club on swinging 52nd Street. Harry's case: the gangland-style murder, right in the Onyx (while Art Tatum plays) of ambitious young hood Joey Seldes--whose sexy widow (""I kissed her hard"") hires Harry to sleuth. So he follows a couple of slender clues, linking Joey not only to a diamond heist but also to N.Y.'s homosexual underground and the Nazi party. Some of this legwork is neat and vivid; some of it just contrived--as Joey's hectically nefarious life becomes rather implausible. And, like Stuart Kaminsky in the Toby Peters series, Jeffers drops in a cutesy over-abundance of cameo appearances: Gershwin, Whiteman, Jimmie Lunceford, Jimmy Walker, LaGuardia, Walter Winchell, and super-gangster Owen Madden (to whom Harry gutsily says ""Fuck you""). Mediocre as mystery, fairly stylish as a period piece--especially for Jeffers' fellow jazz aficionados.