Sometimes the truth is as slippery as a mermaid ... December, 1925A dark, smog-filled London doesn't seem very Christmassy, or exciting, but then Posie Parker, London's premier female Private Detective receives an urgent call from one of her oldest friends; Rufus, Earl of Cardigeon. Summoned to 'The Mermaid', an ancient hotel in Rye, on the Sussex Coast, in the heart of smuggling country, Posie, together with her husband, Richard, finds her friend in a real state. Rufus has been promised answers about his missing wife, Dolly, but instead there's simply a bizarre string of events: a priceless car mysteriously driven off a cliff; a missing Frenchman, and telegrams from men who simply don't exist. While Richard Lovelace, Chief Commissioner of New Scotland Yard, tries to work out if Rufus himself is the target of a complicated plot, Posie has her own investigations to make. The local tragedy of a missing dancer has been dealt with by county police as an open-and-shut case. But Posie soon discovers it is anything but. And she suspects foul play. And as the snow falls, and Christmas lights go up, secrets are revealed, and Posie becomes involved in perhaps her most personal case so far. She becomes aware that danger lurks at 'The Mermaid', and not just for Rufus. A murderer is on the loose.