The mystery of the episode is introduced in the opening sequence, and the trailer. A elderly woman sees a Mummy in her dining car and dies in 66 seconds. When they find out about it, the Doctor puts it off as nothing. "Old ladies die all the time, its practically in the job description." Once in his own bed, the Doctor convinces himself that there is more to this than just a heart attack.
The Doctor seeks and finds Professor Moorhouse (Christopher Villiers, appeared in The Kings Demon's 1983 with 5th Doctor) , an expert on alien mythology. He drills the Prof for info on The Foretold, as he offers a Jelly Baby, and another person dies.
The analog clock is a great touch, to the mystery and the flavour of the setting aboard the Orient Express. The Doctor's cold and callous demeanor upsets Clara and she puts her foot down, telling Maisie the truth, that the Doctor can't save her.
A lot of people on the net are upset about this, this was Clara's exit, her final nail in the coffin as to why she was leaving. What has been missed is the Doctor's redemption in the final five minutes.
Why did he do it? Why is he so cold? Why is he heartless? There was, and always has been, a reason.
In the end this was a good episode that sees a turn in Clara's perception of the Doctor.
Doctor: I'm the Doctor and I'll be your victim this evening, are you my Mummy?
Doctor: Sometimes the only choices you have are bad ones, but you still have to chose.
Next time on Doctor Who: Flatline