A Killer's Essence — Dave Zeltserman

Stan Green is a New York City Homicide Detective who has seen better days. As his family life threatens to disintegrate and his work partner disappears, he is assigned to the most shocking case of his career-a strange and remarkably violent murder. Stan must look into the crime alone. He finds just one witness, a neurologically disabled recluse who sees through the souls of others as demonic hallucinations. As more murders occur, and he drifts further from his family and friends, Stan's suspicion and rage escalate. Soon he realizes that the deaths fall into the pattern of a serial killer--and starts to believe that his witness is not at all insane, but terrifyingly perceptive....