Strong Poison by Dorothy L. Sayers

Harriet Vane, a noted mystery writer, was on trial for causing the poisoning death of her lover, Philip Boyes. He had died from arsenic poison and Ms. Vane had procured arsenic which she said was research for the mystery novel which she was currently writing. The trial went to the jury. The jury could not come to a decision, and the judge decided that another trial would be held in one month's time.

Lord Peter Wimsey was in the audience at this trial and he was determined to find the killer of Philip Boyes during that month, because he was in love with Harriet Vane and was going to marry her. She, however, did not know this, and did not really believe Lord Peter when he told her of this.

Lord Peter received a lot of help in finding the murderer from the secretarial bureau which was managed by Miss Climpson. This bureau, otherwise known at the Cattery, did indeed do secretarial work but some of its employees did undercover work for Lord Peter who was the real owned of the Cattery. First Miss Murchison was employed as a secretary for Mr. Norman Urquhart who was the cousin of Philip Boyes and the legal representative for their rich great aunt. Miss Murchison also received special training in lock picking from a reformed burglar who had found religion.

Then Lord Peter sent Miss Climpson on an especially delicate mission to find the will of Philip Boyes' aunt, because Lord Peter felt that the identity of the murderer was directly related to the terms of this will. Miss Climpson engages is a very humorous subterfuge in order to succeed in her mission. It should also be noted that Bunter, Lord Peter's man does a bit of investigating himself.

This book was published in 1930 by Dorothy Sayers and was her fifth mystery novel. It was on the list of the 100 best mystery novels of all time by the Mystery Writers of America.