Agatha Christie’s novel Curtain describes Hercule Poirot’s departure. It’s also a departure from Christie’s usual subject matter if not her writing style or general sharpness: the typical plot is turned on its’ head as Poirot, confined to a wheelchair and suffering from severe angina, already knows the identity of the killer he is tracking, although not his victim, and is racing to solve an impossible crime that has yet to be committed. The killer’s identity is concealed from Hastings, who must act as Poirot’s eyes ears and hands, precisely because he is too reliable a narrator. Physically lightweight, and as short and succinct as Christie's other novels, the characters constantly debate the morality around issues of life and death, and Poirot's disapproval of murder is tested. The novel was written in the 1940s but at Christie’s request was only published in 1975, the year before her death.
Most of Agatha Christie’s fiction centres not on pathological killers but on crimes of passion, necessity, or desperation committed by people who are not so unlike the rest of us. Given the time of writing, it is striking that in Curtain Christie has written both a serial killer novel and a sci-fi cross-over. Whereas today we are used to the serial killer concept and question it far less than perhaps we should, in the 1940s this would have been a relatively exotic concept and the novel takes time to justify the killer’s psychopathy, along with an explanation of a highly speculative method of killing, in psychological terms. At the same time the novel is consistent with – and explains – Christie’s reoccurring theme that anyone can be a murderer.
You can read more about the novel here – but serious spoiler alert: only follow this link if you have already read Curtain.