The Watchman by Robert Crais

A wild-living young heiress slams into trouble in the L.A. night—the kind of trouble even her money can’t shut down. After her Aston Martin collides with a mysterious car, Larkin Conner Barkley attempts to help the accident victims—and becomes the sole witness in a federal investigation. Whisking her out of her Beverly Hills world is Joe Pike—ex-cop, ex-Marine, ex-mercenary—hired to shield Larkin from a relentless team of killers. But when a chain of lies and betrayals tightens around them, Pike drops off the grid and follows his own rules for survival: strike fast, hit hard, hunt down the hunters. . . .