Inspector Neele is a methodical Scotland Yard detective assigned to investigate the sudden death of Rex Fortescue. While many assume he is unimaginative due to his plain appearance, he possesses an analytical and highly observant mind. Growing up on a traditional estate, he views the wealthy Fortescue family with class-conscious skepticism. He relies on factual evidence but learns to appreciate unconventional insights.

Miss Jane Marple is an elderly spinster from the village of St. Mary Mead who operates as an astute amateur detective. Outwardly unassuming and frequently underestimated due to her age, she uses her deep knowledge of village life to identify human behavioral patterns. She travels to the Fortescue home out of concern for her former maid.

Rex Fortescue is the wealthy patriarch of the Fortescue family and the head of a London financial firm. He is widely disliked by his family and employees due to his tyrannical behavior and ethically dubious business practices. He recently married a much younger woman and lives in a lavish suburban mansion called Yewtree Lodge.

Lance Fortescue is Rex's estranged younger son who unexpectedly returns to Europe from Kenya. He is cynical and openly critical of his family's conventional, money-driven lifestyle. Despite his rebellious exterior, he presents himself as a devoted husband and frequently clashes with his older brother over the family firm.

Pat Fortescue is Lance's sociable new wife, possessing aristocratic ties in Ireland. Having lost two previous husbands under tragic circumstances, she is anxious about her arrival at Yewtree Lodge. She feels deeply uncomfortable in the lavish mansion and quickly befriends Miss Marple.

Percival is Rex's eldest son and a partner in the family financial firm. He is highly frugal, obsessed with order, and views the murder investigation primarily as a frustrating disruption to his business operations. He lacks social grace and maintains a frosty relationship with his younger brother.

Jennifer is Percival's wife and a former nurse who is looked down upon by the Fortescue family for her middle-class origins. She feels bored and isolated in her marriage. The murder investigation breaks the monotony of her life at Yewtree Lodge, giving her a grim sense of fascination.

Miss Mary Dove is the demure, young, and highly efficient housekeeper at Yewtree Lodge. Beneath her professional exterior lies a sharp observer who openly admits to working for the Fortescue family purely for the generous salary. She manages the estate with absolute precision.

Gladys Martin is a naive and highly credulous young parlor maid at Yewtree Lodge. Raised in an orphanage and formerly trained by Miss Marple, she is easily distracted by sensational magazine articles. She handles Rex's clothes, making her an early subject of police questioning.

Miss Ramsbottom is Rex's elderly sister-in-law from his first marriage. She lives as a recluse in Yewtree Lodge, avoiding the rest of the household due to her general misanthropy. She views the tragedies befalling the family as divine retribution for their moral decay.

Adele is Rex's glamorous second wife, significantly younger than her husband. She is heavily motivated by luxury, showing little genuine grief over Rex's death as she anticipates inheriting a massive sum of money. She relies heavily on her golf instructor for emotional support.

Elaine is Rex's unmarried daughter and the only family member who shows genuine grief over his death. However, his passing also grants her financial independence. She plans to use her new wealth to pursue a marriage her father previously forbade.

Vivian is a golf instructor whose relationship with Adele Fortescue goes beyond professional lessons. He is highly anxious and terrified of being implicated in the police investigation. He relies on Adele to conceal the true nature of their association.

Gerald is a radical schoolteacher who despises capitalist wealth but is eager to marry Elaine Fortescue now that she has come into her inheritance. He plans to use her assets to fund a progressive school.

Crump is the butler at Yewtree Lodge. He is unreliable and prone to drinking. The housekeeper keeps him on staff primarily because his wife is an exceptionally skilled cook.

Mrs. Crump is the highly skilled cook at Yewtree Lodge. She is deeply proud of her elaborate meals and easily frustrated by the other staff members' lack of professionalism.

Ellen is an elderly and opinionated housemaid at Yewtree Lodge. She views the family's misfortunes as a natural result of their general moral decay and is particularly disgusted by Adele's behavior.

Miss Grosvenor is Rex Fortescue's attractive young secretary. She is the one who discovers his medical emergency. She insists to the police that she followed her exact daily routine when preparing his beverage.

Miss Griffith is an older, experienced secretary at Rex Fortescue's firm. She is aware of the family dynamics and Rex's increasingly erratic business decisions.

Sergeant Hay is Inspector Neele's subordinate officer. He assists with interrogations, searches Yewtree Lodge for evidence, and manages the logistical details of the police investigation.

Dr. Bernsdorff is the medical examiner and a colleague of Inspector Neele. He provides crucial medical insights into the unusual nature of the taxine poison used in the case.

Mrs. Mackenzie is the widow of Rex Fortescue's former business partner. Following her husband's suspicious death at an African mine, she swore vengeance against Rex. She now resides in a psychiatric sanatorium.