A woman, identified by the film’s title, sits burdened with bags and bothered by a moth while waiting for transportation. She gets on board to discover two other travelers playing chess in an unusual way – their moves are determined by how the train travels along the rails and scoring points! The rest of the people on board seem like a very odd group, and as she observes them, she begins to imagine what one might have been like before he acts inappropriately toward her. The train comes to a halt, and everything is still within this increasingly strange reality. The woman—who reminded me somewhat of Isabella Rossellini—is dressed in a twinset and pearls reminiscent of the 1920s. The technology seems modern or even advanced, and slowly her anxiety about traveling begins to affect us as viewers. The quality of the character animation is remarkable, and the level of detail – particularly in the faces – can be quite striking and unsettling at times. Where is she headed, and who or what accompanies her? What’s the meaning of the green mist? And that moth—what's its purpose? "Horror Express," be warned...!

Source on TMDB