Tansy Clark is in her mid thirties, an independent woman with a pleasant house in Chelsea, a retired police inspector father whom she frequently visits as well as a close friend, Frank Cartwright, a journalist. But this is London in the eighteen seventies and the Thames that flows at the bottom of Tansy's garden yields macabre secrets. It is beside the river that Tansy meets Verity, a young woman who has recently rented a house in the neighbourhood and who waits anxiously for a missing husband to return. In trying to help the lonely young wife Tansy is enmeshed in a dangerous and involved puzzle, which will lead her into the murky outposts of the East End. Now not only her friendship with Frank Cartwright is threatened, but also her own life.