The story is set in New York City, 1896. A serial killer is on the loose. He is preying upon cross-dressing boy prostitutes. Police detectives are making no progress solving the guesome crimes. In fact, someone with power or influence seems to be bent on silencing witnesses and thwarting any investigation. Reform-minded police commissioner Theodore Roosevelt (yes, the same TR who later became president), determined to catch the killer, assembles an unconventional group of investigators headed by “alienist” Dr. Lazlo Kreizler. (In the 19th century, when psychology was in its infancy, the mentally ill were considered “alienated” from themselves and society, and the experts who treated them were known as “alienists.”)

Dr. Kreizler’s team includes his former Harvard classmate, New York Times crime reporter John Moore; Moore’s longtime friend, spitfire heiress-turned-NYPD-secretary Sara Hamilton; and two former mental patients who now work as his servants.

To help identify the killer, the team attempts to develop a psychological profile of the type of person who would be capable of such horrendous deeds. The novelty of their approach does not win them any fans from the mental-health establishment or most NYPD detectives, and throughout the novel, they attempt to keep their involvement secret.

Author Caleb Carr puts his background as a historian to fascinating use. “The Alienist” is filled with rich details about both the seamier underside and more privileged parts of late-19th-century New York City. It also details the then-novel crime detection techniques. Detectives Lucius and Marcus Isaacson, assigned to assist the investigation, employ the not-yet-accepted science of fingerprinting and other methods of identification in their hunt for the killer.

“The Alienist” is one of the Most enjoyable murder mysteries that I have ever read. The characters are memorable, dryly amusing at times, and always fascinating. The plot moves along at a brisk pace and the historical detail does not bog it down. Lovers of historical fiction and detective mysteries will find a treat in “The Alienist.”