Let us see, Mr. Clever Poirot, just how clever you can be.' Murder is a very simple crime. But in the hands of a maniac, a serial killer, it becomes a very complicated business. With the whole country in a state of panic, the killer is growing more confident with each successive execution?Mrs. Ascher in Andover, Betty Barnard in Bexhill, Sir Carmichael Clarke in Churston... But laying a t…