Phyllida Moon’s contract with the Independent Theatre Company and her marriage to its stage manager come to an end together, and when the Company moves on she stays behind in the seaside town where they played their last engagement of the summer season. To help her feel at home in her role as a private eye in a forthcoming TV series, Phyllida finds a job with a real-life detective agency where she sleuths in character, entering the life of the unhappy Brian Fletcher as two very different women. Fletcher is under suspicion from a neighbour of abusing his adoptive daughter, the cool and enigmatic schoolgirl Judith, and displays the tension of a guilty man. . .

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 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.