When PI Phyllida Moon returns to Seaminster, after a trip to Scotland which changed her personal life for ever, the Peter Piper detective agency has a nice little job ready and waiting for her. Hugh Jordan is suspicious about just how many late night meetings his wife, Sandra, is having with her business partner - while Sandra is worried about whether there is more to Hugh's many choir rehearsals than meets the eye. Phyllida employs her wide variety of disguises to investigate the Jordans' world: the spinsterish Miss Spence joins the choir, and the amicable American, Mrs Parker, befriends Sandra. These masks may succeed in being impenetrable - but the Jordan family, it turns out, is every bit as enigmatic.