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 Jordan's world: the spinsterish Miss Spence joins the choir, and the amicable American, Merle Parker, befriends Sandra. These masks may succeed in being impenetrable -- but the Jordan family, it turns out, is every bit as enigmatic.