The Case of the Runaway Girl by K.B. Owen

Lady detective Penelope Hamilton must navigate a labyrinth of 1880s politics, high society, and murder.

On a January night in 1887, trouble comes knocking at Pinkerton detective Penelope Hamilton's door in the form of a sulky young runaway. The girl turns out to be the grandniece of an influential senator, who hires Pen to escort her and her friend from Chicago to his Washington, DC home.

What seems a simple assignment takes an alarming turn when a hired thug shadows them on the train, and Pen stays on the case in Washington for the girls' safety. But in the days that follow, the senator's home is broken into, his driver goes missing, and she is pursued along dark city streets and nearly captured. Obviously, Miss Hamilton is thwarting someone's plans, and such an encumbrance must be removed.

In a search for answers to keep herself and her young charges safe, Pen must tread carefully within the confines of 1880s back-room politics and business tycoons with a lot to lose, while resisting the attentions of an attractive but not-quite-reformed jewel thief who knows far too much about her.

She'll need more than her lockpicks and derringer this time, if she is to save them all. 

THE CASE OF THE RUNAWAY GIRL is the third adventure in the CHRONICLES OF A LADY DETECTIVE series featuring 1880s Pinkerton detective Penelope Hamilton.