Detective John Hooper, William Monk’s right-hand man at the Thames River Police, has fallen in love with Celia, the cousin of the victim in their most recent murder case. Now Celia has discovered that the man her good friend plans to marry this Christmas is far from what he seems. His first marriage ended with his wife walking into the sea – not of her own accord – and Celia hopes Hooper can help show her friend the truth.