This one I found on a Christopher Lee box set of horror movies...or was it Peter Cushing? One of them. They were only in 80 movies together.
Horror Express is about a scientist (Lee) who finds what he assumes is the missing link and brings it onto a train upon which his frenemy Cushing is also traveling. After a series of weird murders, people begin to suspect the creature is doing all the damage. There is a Count and Countess aboard, as well as their spiritual advisor (think Rasputin). Later, Telly Savalas shows up as a military officer with a detachment of soldiers looking for rebels. When the creature from the box gets killed about halfway through the movie, the real wackiness begins until we somehow have an all zombie finale.
I was surprised by how creative and twisty this old b-movie is. Like I said, killing the thing in the crate is really just the beginning of the trouble on the train. Like other train bound movies, the single setting helps everything feel claustrophobic. Cushing and Lee do a great job as rivals who help each other figure out what the hell is going on.
While this won't win any awards, it is better than you think it would be. I would give it a C+. Check it out if you like obscure 70s horror.