A reproduction of the Orient Express was built that travelled in space. It attempted to recreate the land-based Orient Express down to the fine details, with some omissions. (TV: Mummy on the Orient Express)
The Eleventh Doctor received a call requesting his presence as it was having trouble with an "Egyptian Goddess" who had escaped from the Seventh Obelisk. (TV: The Big Bang)
Eventually the Twelfth Doctor heeded the request, confessing to Clara Oswald that he knew they were being lured into a trap. The Foretold, a mythical mummy, was onboard and murdering passengers.
The Doctor soon deduced that all the passengers on the train were experts and scientists who had been gathered to study the Foretold. The dining car revealed itself to be a white laboratory as Gus - the trains computer - halted the train and revealed that the whole scenario was set up in order to find out more information about the Foretold.
After several deaths aboard the train, the Doctor explained the mummy to be a soldier, waiting to be dismissed from his duties. When the Time Lord attempted to find out who had organised the gathering on the train, Gus blew up the Orient Express and all evidence of who had summoned him and the other scientists. (TV: Mummy on the Orient Express)