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.