The Angel of Darkness is a 1997 crime novel by Caleb Carr[1] that was published by Random House (ISBN 0-7515-2275-9) and is both a sequel to The Alienist (1994) and the second book in the Kreizler series.

Set in 1897, Dr. Laszlo Kreizler's associate, Sara Howard, now a private detective, comes to him for help in locating Ana Linares, the kidnapped infant daughter of a visiting Spanish dignitary.

The mystery is complicated by rising tensions between Spain and the United States, and war in Cuba seems inevitable.

Their search for the missing child leads them to contact with an enigmatic woman with a murderous past, who enjoys the protection of the Hudson Dusters, a notorious gang.

The series stars Daniel Brühl, Luke Evans, and Dakota Fanning as an ad hoc team assembled in mid-1890s New York City to investigate a serial killer of street children.