London 1811. To protect the dubious reputations of both himself and a popular courtesan, bored Lord Roderick Davenant, head of a disreputable family, takes home Addy, a climbing boy (sweep's apprentice), who accidentally falls down the bedroom chimney during a sexual encounter.
Consigning the boy to the care of his servants, Davenant forgets about him. It is left to his groom Henry to discover that Addy is no ordinary climbing boy: he is literate, speaks fluent French, has the manners of a gentleman and says he lives in "a castle" with his grandfather. Henry is convinced Addy is the victim of "a jacketing concern," underworld slang for someone usurped from his wealth. At first sceptical, about this, Davenant changes his mind about Addy when he discovers the boy knows Latin.
An inveterate gambler, Davenant accepts a wager to find Addy's family from a young man with a grudge against him. From the start murder and danger dog Davenant's quest. Someone seems to know his every move. Why is a man with buckled shoes following him? Why is a pedlar watching his house? Why is a sinister duke so interested in Addy? Who wants Addy dead? And why?
With help from Bodger, a cheeky climbing boy; Verity Barclay, an attractive Quaker heiress, and Henry, Davenant goes from fashionable Mayfair to London's underworld and Sussex smuggling haunts seeking answers, only to discover they are to be found much closer to him than he realises.