Lt. Sam Holland and her team are plunged into another complex case that at first seems routine. But as Sam tugs on the threads of the investigation, she uncovers a deep, dark Washington secret that threatens the careers of some of the government's highest-ranking officials. Racing to catch a killer before he can strike again, Sam and her fiancé, U.S. Senator Nick Cappuano, attempt to plan a wedding while her colleague Detective Tommy “Gonzo” Gonzales faces life-changing news.