Critical Impact (Whisper Lake) by Linda Hall

The bomb wasn't supposed to be real. But the mock-disaster explosion to test emergency procedures killed two people in a small Maine town. And all evidence points to shy makeup artist Anna Barker as the prime suspect. When Deputy Sheriff Stu McCabe is assigned to investigate the case, Anna hopes he'll prove her innocent. But with a harrowing past of his own, Stu seems to trust no one. Something that might save both their lives when the real killer plans to make critical impact—again.