This is a Hercule Poirot Mystery first published in 1933.
The killer devised an elaborate plan to throw Hercule Poirot off the scent of tracing the killer of Lord Edgware. Suspicion was first levelled at his estranged wife because this beautiful American actress Jane Wilkinson had been seen going into the mansion of Lord Edgware at the time of the murder. Did Jane Wilkinson kill her husband who had refused divorce from her? What was puzzling was that Jane Wilkinson was at a dinner with Sir Montagu Corner in his house at around the time of the murder.
If it was not the wife Jane Wilkinson, who else would want Lord Edgware dead? The famous Belgian detective Hercule Poirot and his friend Captain Hastings had to chase for leads by interviewing various persons connected with Lord Edgware and his wife Jane Wilkinson. It got even more muddled as I read the pages of the book. The author Agatha Christie kept up the suspense by making Poirot puzzled for a long time as he moved on in his investigation till the end.
At the end, it was really simple how the killer did it. Agatha Christie made me think otherwise.