In 1897 Stevie Tagget, a reformed street urchin is with PI Susan Howard when someone comes up to them in a frantic manner and tells them that her child has been kidnapped.
Her husband is secretary to the Spanish Consul and since the U.S.and Spain are close to war, they don't want to report a kidnapping in case it would worsen the relationship between the two countries.
The group asks their friends Lucas and Marcus Isaacson for help.
They learn that a woman has been attacked and they get a police sketcher to draw a likeness to the attacker.
They learn that a there was a nurse investigated in the past and she worked in a hospital where a number of infants under her care have died in similar respiratory ailment as a child under the nurses care now.
The book is extensive in detail, going through the steps to find the child, traveling through New York City and upstate. The characters are very realistic as is the authors descriptions of New York.