Captain Lacey is asked by Thompson of the Thames River Police to help him investigate a cold case–the murder of a woman found near the docks Thompson patrols. The investigation was sidelined, considered unsolvable, but Thompson, in touch with the woman’s family, has long wished to find her murderer. Captain Lacey joins him in the hunt, entering a part of society that is closed to outsiders. Meanwhile, he must deal with his daughter’s debut and more developments in his new domestic life.