And Then There Were None (1945)
Rene Clair's 1945 Agatha Christie adaptation. The template for every isolation murder mystery since.
Dudley Nichols wrote Stagecoach, The Informer, Bringing Up Baby and For Whom the Bell Tolls, and worked repeatedly with John Ford across a long partnership.
He won Best Screenplay for The Informer and declined to accept it, in solidarity with the Screen Writers Guild during its dispute with the studios, making him the first person to refuse an Academy Award.
Stagecoach is the enduring script, a group of strangers in a confined space whose social ranking inverts under pressure, which is a structure the Western used for decades afterward.