This would have been better without some completely pointless changes brought in to the plot. At the start there is a completely implausible attempt to suggest that Mark is suspected of being the killer. Nothing in the show suggests the police would suspect him in this way and the plot line dies quietly, having wasted a fair amount of time. Most of the performances are adequate at worst but the dialogue is often poor. One of the things which made the book successful was the way it at least played with the idea of the supernatural. No one could be fooled by the witches here. Agatha Christie was usually luckier than this in her adaptors for the screen.