Books like St. Peter's finger by Gladys Mitchell

When Ursula Doyle, a student at the secluded convent and girls’ school of St. Peter’s Finger, dies in a filled tub, the coroner determines it was carbon‑monoxide poisoning. Mrs. Beatrice Lestrange Bradley, a renowned detective, is summoned by her barrister son to unravel the case. As Bradley delves into the convent’s precise but limited information, she confronts a web of suspects: Ursula’s aunt Mrs. Maslin, who stands to inherit hers; Miss Bonnet, a visiting physical training mistress; cousin Ulrica, an enigmatic girl with religious mania; and Sister Bridget, who has a penchant for starting fires. With each revelation, the question of whether the death was an accident or a deliberate murder deepens. Bradley must navigate the convent’s strict hierarchy and eventual conspiracy to prevent another tragedy while protecting herself from harm.

First publish date: 1972