This is the best book I've read so far in my stack of novels about organ donation. A completely original idea told with skill and verve. Terry McCaleb is an ex-FBI agent who's recently had a heart transplant. He's minding his own business recuperating on his boat when a woman comes to see him asking for his help to find the killer of her sister. He insists he doesn't want to get involved, but she says he has to - his heart came from her sister. Knowing he has benefited from a cold blooded killing is hard enough, but little by little McCaleb pieces together evidence from apparently random shootings and uncovers a plot, sinister, devious, and emotionally challenging which puts him in real danger. My only gripe is that it's highly unlikely someone could accomplish what McCaleb did shortly after a heart transplant, but otherwise it's a compelling read.