A group of students head over to a remote village in rural Yugoslavia to witness an ancient pagan ritual, that they only perform every 100 years. But unfortunately, it seems their guide, Professor Andromolek (Bo Svenson) has an ulterior motive for inviting them, as they find they're not there to witness the ritual, but be the central part of it...
Seems this has something to do with human sacrifice, and not too keen on the prospect of being burned alive in a sacrificial pyre, they manage to escape and hop onboard a passing train. But it seems their problems are far from over, as the rear passenger cars subsequently uncouple themselves, and the train driver and conductor are killed in a freak "accident", leaving them stuck on a runaway train.
Lots of weird supernatural stuff ensues, as the train refuses to slow down. When the railway workers try to stop the train by derailing it, the train manages to continue to travel alongside the track unabated, then jump back on the rails, as well as coming through a head on collision with another train without so much as a scratch. As the unfortunate students on board desperately try to find a way of stopping it.
Kind of a bizarre mash up of The Wicker Man (1973) and Runaway Train (1985), this was renamed "Beyond the Door 3" for it's US release, to capitalise on the success of the previous 2 films, although this and the other films are completely unrelated to each other.
Bit of a strange one, it's worth a watch, despite some dodgy model work. Although I can't help but wonder if the producers of "Midsommar" (2019) got some ideas from the film's opening premise.