John Carter, a Bow Street Runner (detective) in London, is called to the deathbed of the Third Duke of Bedford who tells him a disjointed story and hands him an envelope which holds a couple of documents. One is an account of debts, another is a deed to a house. Carter has no idea what to make of this odd inheritance – if inheritance it is. But since he made a deathbed promise to the duke to "Carry it through" – whatever that could mean – he intends to use his detective skills to piece together the puzzle of the duke's story and the documents.
Serena Marsh came to London to help straighten out the tangled finances of her Aunt Diana's fashionable gambling hell and found a not-quite-proper-but-not-quite-improper way of paying off her aunt's debts held by the Third Duke of Bedford.
Carter has enough information at hand to seek out Miss Marsh. When he discovers her method of paying those debts, he is a very surprised and admittedly happy man.
But the puzzle of the duke's story and the documents in his possession remains. And he needs Miss Marsh's help to sort it all out. She is not going to be happy when they get to the bottom of it. And he is going to need much more than good detective skills to get what he wants in the end: her love.
