Helga Allowby, a self-described spinster, has been accused of sending noxious poison pen letters to the residents of her village and she wants Hetty to prove her innocence. Hoping to penetrate the mistrust that pervades the village, Hetty goes undercover as Tara Hall, a visiting painter. When Hetty turns up next on the mailing list, she suspects that Miss Allowby is guilty of bad penmanship.

Hetty is called in to investigate when one by one, the contestants in the Blainthorp Muiscal Festival lose their voices. The sponsor of the festival, Oliver Hardiman wants the mystery solved but Hetty only has five days.She finds herself caught up in a battle between rival pharmacists who may be using their skills to harm the finalists.

Hetty is called in by the Mayor of Titterslow to look for his daughter who has runaway. She has learning difficulties and the Mayor and his wife want the matter of her disappearance to be kept very quiet. Hetty discovers that she left with her boyfriend, Bernard, who also has learning difficulties and that they were making their way to a country hotel.

Hetty gets mystical as she investigates Maurika Rome, a spiritualist suspected of using séances and blackmail to prey on the savings of the recently widowed. When Hetty goes undercover and invents a late husband she wishes to contact, she begins to wonder if Mrs. Rome isn't the real thing - until a woman claiming to be her "late husband's" illegitimate daughter shows up demanding money. Geoffrey's secret romance with Rome's daughter, Sara, threatens to undermine Hetty's carefully laid trap and nearly causes him to quit the agency.

The children of well-to-do widow Gillian Snape are worried that her photographer-fiancé Lester Rose is marrying her for her money, and hire Hetty to investigate Rose's past. With Geoffrey's help, Hetty learns that Rose is a gambler and a gigolo with several previous identities. Surprising facts revealed by two women from his past and Hetty's tense undercover visit to his studio expose a somewhat less thorny side of the man. Still, is he the marrying kind?