London 1940: As the Blitz rages and her future is threatened by fallout from the war, Agatha Christie (Helen Baxendale) makes the decision to kill off her most famous creation. After twelve Poirot novels in six years, Agatha should be a rich woman. Instead, she's struggling to make ends meet. Killing Poirot in the midst of this turmoil seems almost spiteful, but Agatha has a plan: she's selling the novel to a private buyer, a super-fan who will pay anything to own a piece of history. A meeting at an infamous London hotel is arranged, where despite the presence of an old friend, things quickly go wrong. As the bombs fall and the bodies pile up, the real danger of her situation becomes apparent: the only thing more valuable than the last ever Poirot novel is the last ever book written by Agatha Christie.