London, 1838: the controversial practice of Mesmerism, with its genuine practitioners and its fraudulent chancers, has hypnotised the city. Miss Cordelia Preston, a beautiful, ageing, out-of-work actress terrified of returning to the poverty of her childhood, suddenly emerges as a Lady Phreno-Mesmerist. In her candle-lit Bloomsbury basement she learns to harness her talent - and to finally look towards the future.

But success is fragile when you have a past filled with secrets. On a wintry, moonlit night a body is found in Bloomsbury Square, and what began as an audacious subterfuge erupts into a scandal. Cordelia's past is revealed, bringing not only heartache but terror - and the mystery of a cloaked figure who waits for her in the shadowy London streets.