What happens when evidence emerges that New York City’s most notorious vigilante — a Robin Hood type who bumps off drug lords and dubs himself Justice — might just be a cop? That’s the daunting question facing crackerjack detective Brian McKenna, who must piece together the increasingly complex puzzle on little more than adrenaline and coffee. And the headaches don’t stop there: He’s got a nosy reporter on his back, and he’s also trying to parse the intentions of his partner, Cisco Sanchez, a braggadocio who may or may not know Justice’s true identity. Former NYPD captain Mahoney displays a well-honed knowledge of the give-and-take of tough investigations — at times, this absorbing novel reads like a police procedural handbook. It’s his ear for sharp dialogue, though, and propensity for narrative surprises that make this taut, timely story such a thrill.