In New York, Dr. Kay Scarpetta, chief medical examiner, matches wits with a sadistic killer who operates in the subway tunnels. After killing a transit policeman he infiltrates the FBI's computers and sends her taunting messages while continuing to kill. The Central Park (New York) murder of a young, homeless woman on Christmas sends medical examiner Scarpetta, her friend Captain Marino, & her niece on a chase that ends in the subway.