Life is good for Kit Marshall. She's a staffer in D.C. for a popular senator, and she lives with an adoring beagle and a brainy boyfriend with a trust fund. Then, one morning, Kit arrives at the office early and finds her boss, Senator Langsford, impaled by a stainless steel replica of an Army attack helicopter. Panicked, she pulls the weapon out of his chest and instantly becomes the prime suspect in his murder.

Circumstances back Kit's claim of innocence, but her photograph has gone viral, and the heat won't be off until the killer is found. Well-loved though the senator was,...