"Living a quiet life of semiretirement with Kai, his new wife, Murphy is called back into action by President Arthur to assist the New York City police with a serial killer on the loose in the city streets. What baffles the police most is that the killer is using a .36 caliber cap-and-ball revolver to kill his victims with, a weapon that has been obsolete since the end of the Civil War. In New York, Murphy is reunited with his old friend Melvin Knoop, a Pinkerton agent who specializes in forensics investigations"--,Provided by publisher.