Unnatural Death by Dorothy L. Sayers - is a 1927 mystery novel by Dorothy L. Sayers, her third featuring Lord Peter Wimsey. It was published under the title The Dawson Pedigree in the United States in 1928.
Lord Peter Wimsey and his friend Chief Inspector Parker are told about the death, in late 1925, of an elderly woman named Agatha Dawson who had been suffering from terminal cancer. She was being cared for by Mary Whittaker, her great-niece and a trained nurse. Miss Dawson had an extreme aversion to making a will, believing that Miss Whittaker, her only known relative, would naturally inherit everything. Wimsey is intrigued in spite of the fact that there is no evidence of any crime (a post-mortem found no sign of foul play), nor any apparent motive (on Miss Dawson's death her estate did indeed pass, as she had expected and wished, to her great-niece).
Wimsey sends his private investigator, Miss Katharine Climpson, to the village of Leahampton to investigate. She discovers that shortly before her death Miss Dawson had dismissed her maids, the sisters Bertha and Evelyn Gotobed. Wimsey places advertisements in the press asking them to get in touch. A few days later, Bertha is found dead in Epping Forest. On the body is a £5 banknote, originally issued to a Mrs Muriel Forrest who lives in an elegant flat in South Audley Street, Mayfair. Wimsey and Parker visit her. She claims not to remember the banknote, but thinks she may have put it on a horse. Wimsey tricks her into providing her fingerprints on a wineglass. In a drawer he finds a hypodermic syringe with a doctor's prescription "to be injected when the pain is very severe".
Evelyn Gotobed tells Wimsey of an episode shortly before the sisters were dismissed in which Miss Whittaker had tried to get them to witness Miss Dawson's will, without the latter's knowledge. A mysterious West Indian clergyman named Hallelujah Dawson had also turned up, claiming to be an impecunious distant relative.
Mrs Forrest asks Wimsey to visit her at her flat in London where she clumsily makes advances to him. Wimsey suspects blackmail. He kisses her and realises that she is physically revolted by his caress.
Wimsey discovers a motive for Miss Dawson to be killed before the end of 1925: a new 'Property Act' coming into force on 1 January 1926 will change the law of inheritance, resulting in an intestate's property no longer passing to a closest-relative great-niece but being forfeit to the Crown. Much play is made of a fictionalised uncertainty in the meaning of the word "issue".