Strong Poison by Sayers

 Strong Poison is the first book with Harriet Vane in it, and it reflects part of Sayers' own life.  It is a murder mystery about arsenic poisoning.  Harriet, like Sayers herself, is a Bloomsbury writer who writes murder mysteries, and like Sayers she falls in love with a young man.

Philip Boyes, her lover, is a poet and novelist, like Sayers' boyfriend John Cournous, and like John he tells her as John told Sayers, that he does not believe in marriage and does not want a conventional married life with children.  Boyes pesters Harriet to live with him and she finally agrees, and moves  in with him.  Boyes like Cournous is pretentious, a good writer but someone who likes to show off his intellectual abiliites, and who resents Harriet for earning a living for both of them, though the money comes in handy.  

Dorothy did not live with John Cournous, but she did have an intimate relationship with him while still hoping that he might marry her.  She got tired of his ways, and broke off with him because, although she cared for him, she could not see any future in it.  Then she learned that in America, he had married a woman who had children, and gone back on all his principles.  

Harriet finds, after a year, that Boyes also goes back on his principles.  He asks her to marry him and she is angry and upset, since she felt that he had been testing her love for him, trying to see if she would give in to him and abandon her principles for him.   Harriet broke off their relationship and left him.  

Then, Boyes is poisoned with arsenic, and it looks like Harriet, who has been writing a book on arsenic poisoning, might have killed him. 

Sayers used her backstory with Cournous to provide a set up for her murder mystery, and the novel starts with Harriet being tried for his murder. 

Murder stories in Sayers' time were not expected to be fully accurate.  The story would centre around a murder by some esoteric method that was not likely to be used in real life.  In Strong Poison, the murder is poisoning by arsenic, but the killer ate the same food as the victim.  Peter then learn that its possible to build up an immunity to arsenic by eating a bit of it every day and that Norman Urquhart, the murderer had done this, and then shared an omelette with his cousin, the victim. 

Sayers was conscientious about trying to find out scientific information for the methods of murder she used, though she did  not always get it right as she was not a scientist.