Kitty Lucas doesn't like the idea of being her aunt's companion, but it's better than the life of a governess.
On the way to London, she finds herself in charge of a boy left for dead in the road, and solving the mystery of what happened to him is a welcome distraction.
When it turns out he was abducted from school and another boy is also missing - she resolves to pursue the matter, despite the opposition of the enigmatic and infuriating aristocrat, Mr Gregory.
As the conspiracy unwinds, she must break the bonds of her social role and prepare to make a terrible sacrifice.