Jerry is a wounded war veteran and former pilot seeking a quiet recovery in the country on his doctor's orders. Wealthy and sometimes cynical, he rents Little Furze with his sister Joanna to escape city life. He quickly finds himself drawn into the local gossip and becomes emotionally invested in investigating the anonymous poison pen letters.

Joanna is Jerry's attractive, independent sister who accompanies him to Lymstock to aid his recovery and escape her own heartbreak. Accustomed to London life, she finds the village's old-fashioned customs amusing but readily immerses herself in the local society.

Megan is the 20-year-old daughter of Mrs. Symmington from a previous marriage. Socially awkward, poorly dressed, and emotionally neglected by her family, she feels like a complete misfit in Lymstock. Despite her apparent apathy, she harbors deep resentment toward the villagers who judge and exclude her.

Miss Jane Marple is an elderly, unassuming amateur detective visiting Lymstock. Hiding her sharp intellect behind a facade of knitting and polite village chatter, she uses her deep understanding of human nature to quietly observe the townspeople.

Mrs. Symmington is a wealthy, well-respected member of Lymstock society and a skilled bridge player. She dotes on her two young sons with Mr. Symmington but remains emotionally distant toward her older daughter, Megan. She struggles with anxiety and receives medical treatment for her nerves.

Mr. Symmington is the local lawyer in Lymstock and a pillar of the community. Quiet, highly organized, and outwardly calm, he projects the image of a perfectly respectable husband and professional. He is devoted to his young sons but indifferent to his stepdaughter.

Partridge is the dour, middle-aged cook and housekeeper at Little Furze. Originally employed by Miss Barton, she stays on to serve the Burtons. She is strict, fiercely traditional, and often displays a grim attitude toward the other villagers.

Rose is the talkative, emotionally expressive cook in the Symmington household. Described as a plump woman, she is deeply involved in the local rumor mill and often complains dramatically about the stress of her job.

Agnes is a young, naive maid working in the Symmington house. Orphaned as a child, she previously worked for Miss Barton before moving to her current position. She relies heavily on the older housekeeper Partridge for guidance when she becomes anxious about the events in the village.

Miss Emily Barton is a gentle, elderly woman who has lived a highly sheltered life in Lymstock. The last surviving member of a large family of unmarried sisters, she rents out her beloved home to make ends meet and moves into lodgings in town.

Superintendent Nash is the local police officer in charge of investigating the poison pen letters. Soldierly, unassuming, and quietly reflective, he relies on the villagers to help him understand the local social dynamics.

Inspector Graves is an expert from London brought in to assist with the criminal investigation. He has a melancholy enthusiasm for his work and operates on the firm assumption that poison pen writers are typically middle-aged, unmarried women.

Dr. Griffith is the capable but socially awkward local physician. Well-versed in the town's happenings, he worries heavily about the psychological impact the malicious letters will have on the uneducated or suspicious minds of the villagers.

Aimee is Dr. Griffith's vigorous, busybody sister who volunteers heavily in the village. Despite her community involvement, she is deeply judgmental, frequently complaining about the perceived idleness or flaws of her neighbors.

Caleb Dane Calthrop is the local reverend, an absent-minded intellectual who is highly disconnected from everyday life in Lymstock. Prone to quoting Latin, he remains largely oblivious to the village's social tensions and rumors.

Mrs. Dane Calthrop is the energetic, formidable wife of the reverend. She considers it her duty to know the villagers' secrets and maintains an intimidating presence. Frank and unsentimental, she is not afraid to voice her unpopular opinions.

Elsie is the beautiful nursery governess for the Symmington family. Though physically stunning, her conventional personality quickly dispels Jerry's initial infatuation. She is dedicated to the young boys but becomes a target of local gossip regarding her position in the household.