The Marshal (Harlequin Intrigue Series #1543)

His painful past is their present danger 

The last thing US Marshal Brent Thompson needs is distraction from his work. But distraction—in the form of a sexy Chicago investigator—is exactly what he gets. Jenna Hayward is as alluring as she is determined, driven to help apprehend the murderer who killed Brent's mother twenty-three years ago. With a shared mission—and a steadily rising attraction that jeopardizes Brent's resolve to stay unattached—the pair must work together to get answers…before the murderer makes them his next victims.