London, 1905. Margaret Trant lives with her ailing, irascible mother in a dreary boarding house in St John's Wood. The pair have fallen on hard times, with only Margaret's meagre salary from a ramshackle import-export company keeping them afloat.

When a stranger on the tram hands her a newspaper open at the recruitment page, Margaret spots an advertisement that promises to 'open new horizons beyond your wildest dreams '. After a gruelling interview, she finds herself in a new position as a secretary in a dingy backstreet shop. But all is not as it seems; she is in fact working for a highly secret branch of the intelligence service, Bureau 8, whose mission is to track down and neutralise a ruthless band of anarchists known as The Scorpions.

Margaret's guilty love of detective fiction scarcely prepares her for the reality of true criminality, and her journey of self-discovery forms the heart of this remarkable novel, as she discovers in herself resourcefulness, courage, independence and the first stirrings of love.