An old man, Sir Mañuel Camarque, dies when he loses his foothold on a dark winter night, slips into a lake and drowns under the ice. It looks like an open-and-shut case. However...Camarque, who was a world-famous flautist, planned to marry Dinah Sternhold, a woman young enough to be his grand-daughter. The banns of the marriage had just been read for the third time in church and Sir Mañuel was nervous. Dinah tells Wexford that Camarque had suspicions that his daughter Natalie (who would inherit his fortune) was not his daughter at all but an impostor. Wexford investigates, and develops a theory of an intruder who pushed the old man into the lake.