In a Virginia penitentiary, Alex Cross and his partner, John Sampson, witness the execution of a killer they helped convict. Hours later, they are called to the scene of a copycat crime. A note signed 'M' rests on the corpse. Was an innocent man just put to death? Alex soon realizes he may have much to answer for, as 'M' lures the detective out of the capital to the sites of multiple homicides, all marked with distressingly familiar details.