The Crooked Wreath by Christianna Brand

There was a going to be a gathering of the family at Swanswater to commemorate the death of Serifita who was the first wife of Lord March. Lord March had been very much in love with her because she was so beautiful and charming. The family didn't want to be there for this dreary event, but they wished to stay in Lord March's will so they came. There were the cousins, Philip, Clare, and Pita March. Philip was married to Ellen, however Philip had decided that he was really in love with Clare and wanted a divorce. Then there was the troublesome cousin, Edward. Edward was the grandson of Belle who was the second wife of Lord March. She had been his mistress while Serifita was alive, but they married after Serifita's death. Edward Treviss was 18 years old and was convinced that he suffered from mental illness. He had seen a number of psychologists and was convinced that he suffered from fugue states in which he did things which he did not remember doing. The family was also convinced that something was wrong with Edward because he enjoyed telling them about his problems.

The family gathered at dinner. Unfortunately they launched into a discussion of their various complaints and marital complications. Lord March grew so irritated by their arguments that he announced that he was going to change his will that evening, and disinherit most of them. With his present will, Pita would inherit almost every thing with some money amounts going to the others. Lord March said that his new will would leave everything to Belle and Edward and nothing to the others.

Needless to say, the next morning, Lord March was found dead in his study, and the new will, if it had been made, could not be found. The family called upon their friend, Inspector Cockrill, to help them find the murderer. Edward thought that he had done it in one of his fugue states, and the family members seemed to believe that he had done it even if they didn't admit it out loud. What follows are a number of guesses, and hypotheses and suppositions about who in the family had committed the murder. Another murder will occur which further confuses things. The book ends on a very dramatic note with the discovery of the murderer.

I thoroughly enjoyed this book especially the interactions by the family members.  It was published in 1946. I have read it for the 2019 Golden Mystery Challenge in the category of When - Timing of crime is crucial.