The Documents in the Case
Dorothy L. Sayers
 This is an epistolary novel, told primarily in the form of letters between some of the characters. This collection of documents&mdash;hence the novel's title&mdash;is explained as a dossier of evidence collected by the victim's son as part of his campaign to obtain justice for his father. The main narrator, Munting, takes rooms with Lathom, an artist acquaintance. The landlord and downstairs neighbour, Harrison, is a staid, middle-aged widower who has married again; his new wife is young, attractive, passionate and rather foolish. Lathom and Mrs Harrison begin an affair, the husband suspecting nothing, and Lathom paints a remarkable portrait of her. Creeping downstairs to meet his mistress one night, Lathom encounters the Harrisons' live-in spinster companion, who mistakes him for Munting in the dark and makes accusations of assault. Glad of an excuse to leave a situation he finds distasteful, Munting moves away and marries his fiancée, leaving Lathom still in occupation. Lathom's portrait of Mrs Harrison is exhibited publicly, making his reputation on the London art scene. Some time later Munting meets Lathom by chance in London and learns that he is holidaying with Harrison at the latter's isolated cottage in Devon. Harrison's hobby is foraging for wild food, and he is an expert on edible mushrooms. Lathom persuades Munting to accompany him back to Devon, where they find Harrison dead, apparently having cooked and eaten poisonous fungi by mistake. However Harrison's son Paul suspects that Lathom and his stepmother have conspired to murder Harrison, and Munting is drawn unwillingly into the investigation. He discovers accidentally that muscarine - the poison that killed Harrison - can exist in a natural or a synthetic form. The molecules of both forms are asymmetrical; however the natural form is optically active - consisting of only one molecular form; the synthetic form is racemic - with equal quantities of both types of molecule; and the two forms can be distinguished only by using polarised light. The muscarine consumed by Harrison proves to be synthetic, indicating that the mushrooms he ate were poisoned deliberately. Letters between Mrs Harrison and Lathom indicate that she manipulated him into the killing by claiming that she was expecting his child. Lathom is hanged for murder.