Mercy Street — Mariah Stewart

After two high school seniors are shot dead in a park in Conroy, Pennsylvania, the authorities conclude that one of the other two kids in the park that night -- a boy and a girl, both now missing -- was the killer. Private investigator Mallory Russo is hired to figure out what happened and to clear the boy's name. Financing the investigation is reclusive billionaire Robert Magellan, a man who understands the heartache of not knowing what happened to a loved one, having suffered the disappearance of his own wife and infant son a year ago.

Meanwhile, Charlie Wanamaker has traded his job as a big-city detective for one with the Conroy police department. Assigned to the park shooting case, Charlie quickly realizes that the initial investigation left a lot of questions unanswered. Unofficially, he teams up with Mallory to uncover the truth and find the two missing kids, dead or alive. What Charlie and Mallory discover will take them down a twisted path that leads to an old unsolved murder -- and justice for a killer with a heart of stone.