I second the first reviewer :this doc is much too short ;after 1939 , it only mentions "the mousetrap" which is still running in London. There are better movies dealing with the subject.
Agatha Christie's numerous buffs won't learn many things ; the novels are linked to the writer's real life : "the murder of Roger ackroyd" and her disappearance , which has been told told and TOLD ( even a movie was made ,starring Vanessa Redgrave and Dustin Hoffman); her travels on the Orient Express which enthused her and led to the famous "murder" .The first signs of the war and her holidays near an island which spawned the all-time best-seller "and then were none" .
The doc includes extracts of Kenneth Branagh's remakes of "murder on the orient express"and "death on the Nile" ,a MTV episode of Miss marple's investigations ; but the best moments are Sarah Phelps' interventions : she wrote the best adaptation of "and then there were none" for the BBC in 2015. Extracts are included ,notably the scene when the guests are accused by a mysterious voice ....