This movie, as all existent versions of "Ten Little Indians," is based not on the novel by Agatha Christie but on her very similar play. While the identity of the murderer is the same in both versions, the outcome of who survives the murderer's plot is very different.
The poem: Ten little Indian boys went out to dine; One choked his little self and then there were Nine. Nine little Indian boys sat up very late; One overslept himself and then there were Eight. Eight little Indian boys traveling in Devon; One said he'd stay there and then there were Seven. Seven little Indian boys chopping up sticks; One chopped himself in halves and then there were Six. Six little Indian boys playing with a hive; A bumblebee stung one and then there were Five. Five little Indian boys going in for law; One got into Chancery and then there were Four. Four little Indian boys going out to sea; A red herring swallowed one and then there were Three. Three little Indian boys walking in the Zoo; A big bear hugged one and then there were Two. Two little Indian boys were out in the sun; One got all frizzled up and then there was one*. One little Indian boy left all alone; He went out and hanged himself and then there were none. (*In some versions Two Little Indian boys playing with a gun; One shot the other and then there was one.)
The failure of the original copyright holder to renew the film's copyright resulted in it falling into public domain, meaning that virtually anyone could duplicate and sell a VHS/DVD copy of the film. Therefore, many of the versions of this film available on the market are either severely (and usually badly) edited and/or of extremely poor quality, having been dubbed from second- or third-generation (or more) copies of the film.
The trivia items below may give away important plot points.
This has a notably different ending to the original novel which involves all 10 characters ending up dead. Agatha Christie changed how it finished for the theatrical adaptation as she felt that wartime audiences would find it too depressing.
Mr. Owen's identity is foreshadowed twice during the course of the movie. At 32:15, when the men are looking for Mr. Owen, there's a shot of Lombard and Judge Quincannon side by side. Lombard remarks that "Mr. Owen's hand is plain to see", and the judge's hand is the only one visible. In the next scene, it starts raining. Lombard remarks that "all we have to do is keep quiet and we'll hear [Mr. Owen] sneeze." Later, at 49:51, Judge Quincannon sneezes.