After nearly hanging for thievery, Mary Quinn is rescued and educated at Miss Scrimshaw's Academy for Girls. She receives an excellent education, but is unsatisfied with her options for employment in Victorian England. When she expresses her feelings, Mary learns the school is a cover for The Agency, a top secret group of female investigators who assist the Scotland Yard in solving mysteries. Mary joins the Agency and begins her first assignment.
Posing as a female companion for the only daughter of a rich merchant family, Mary seeks to find solid evidence for the family's suspected illegal smuggling. Mary uncovers secrets, but also makes unexpected friends and enemies while completing her first assignment. This is a light mystery, pleasantly low on violence with a nice historical feel. While not entirely believable, the story is entertaining and the characters are well-written.