Lord Edgware Dies

When Lord Edgware is found murdered the police are baffled. His estranged actress wife was seen to visit him just before his death and Poirot himself heard her brag of her plan to 'get rid' of him. But how could his estranged wife Jane have stabbed Lord Edgware to death in his library at exactly the same time she was seen dining with friends? It's a case that almost proves to be too much for the great Hercule Poirot