...otherwise known as Horror Express.
This movie from 1972 stars Christopher Lee, Peter Cushing, and Telly Savalas. All three of them really give it their all. Guy and I watched this movie the other night and it truly delivers. This is a summary from IMDB:
"In 1906, in China, Professor Alexander Saxton discovers an ancient frozen fossil in the remote Province of Szechuan. He brings the remains of the being in a box to Shanghai and boards a trans-Siberian train, where he meets his acquaintance Dr. Wells. During the trip, a life force trapped in the frozen creature is released, killing the passengers."
Sounds dumb, no? But, surprisingly, there are many cool reveals and interesting ideas in this film. The pacing is excellent too. It's action-packed all the way through, but the plot builds somewhat slowly and spookily at first, as the mystery deepens and the action begins to accelerate. By the end of the movie, it's an all-out zombie fest, but it takes a while to get there.