Sarah helps deliver a child to a poor German immigrant, Agnes Otto, on the same day that Agnes learns of the murder of her younger sister, Gerda. Gerda had been what was referred to as a "Charity Girl."

Charity girls came from poor but respectable families; their good times and fripperies, like jewelry and hats, were paid for by men in exchange for sexual favors. Gerda lived that kind of fast life until the night she did not make it home; the next day her badly beaten body was found in an alley.

Agnes is distraught over her sister's murder and Sarah can't assure her that the police will find the killer. In the late 19th century, New York City police do not spend a great deal of time investigating murders unless the victim's family pays them to do so.

So Sarah takes it upon herself to investigate Gerda's demise and soon learns that Gerda is not the first Charity Girl to be beaten to death. She calls upon Detective Sergeant Frank Malloy for help and the two find themselves going to Coney Island and taking a walk on the wild side to find a killer who preys upon poor young women who've gone astray.

While the mystery in Murder on St. Mark's Place is not particularly complex, the process of investigating and revealing the Charity Girl murderer is very entertaining. Sarah and Frank are appealing characters, honest and true to their time; Ms. Thompson develops their budding friendship in small but very satisfying stages.

And, I like the way she leaves you wanting more; I'm looking forward to the next installment in the lives of these two interesting characters. In addition, the author recreates old New York with the kind of detail history-loving mystery-readers really enjoy.

--Judith Flavell