Traitor and the Tunnel — Y.S. Lee

This is the third colourful and action-packed Victorian detective novel about the exploits of agent Mary Quinn. Queen Victoria has a little problem: a series of petty thefts from Buckingham Palace. She calls the Agency for help, and they put Mary Quinn - on her first case as a full-fledged agent - on the case. Going undercover as a domestic servant, Mary's assignment seems simple enough. But before long, a scandal threatens to tear apart the Royal Family. One of the Prince of Wales' irresponsible young friends is murdered in scandalous circumstances and the story, if it became public, would disgrace the young prince. Should the Queen hush things up or permit justice to take its course? Mary's interest in this private matter soon becomes deeply personal: the killer, a drug-addicted Chinese sailor, shares a name with her long-lost father. Meanwhile, James Easton's engineering firm wins a contract to repair some sewers beneath Buckingham Palace. Trouble is, there's a tunnel that's not on