Darkest Fear
Harlan Coben is one of my favorite mystery writers and might I say prolific. His recurring character, Myron Bolitar finds himself in a race against time when he is asked by an ex-girlfriend to track down a reluctant donor for very sick child. She drops a bomb on Bolitar to give him the ultimate incentive to help her. The trail twists and turns as the rush to find the person heats up.