A split-second decision and Brian Darby lies dead. His wife, state police trooper Tessa Leoni, claims to have shot him in self-defence and for Boston detective D.D. Warren it should be an open-and-shut case. But where is their six-year-old daughter?

As D.D.'s homicide investigation ratchets into a frantic state-wide search for a missing child, she must move quickly in order to learn all of Tessa's secrets and understand what has happened to the little girl. But for Tessa, the worst has not yet happened. She is walking a tightrope, with no one to trust and nowhere to turn, as the clock ticks down to a terrifying deadline.

She has one goal in sight, and she will use every ounce of her training to do what has to be done. All that matters is her child and no one could love her more...Two women. With one question...

HOW FAR WOULD YOU GO TO SAVE YOUR CHILD?