Dreadful: (for those wanting the quick version.
OK: we have an orient express snaking through space from side to side: why? Why when it stopped did it go all funny with kinked carriages.
Why was the train there at all. Whoever set it up could just as easily arranged for the train effect in a the 'holodeck' - ARE THEY REALLY SINKING THAT LOW without the need to actually be on a holodeck on a train.
Why was the door from the baggage car coming away from the Tardis in the side of the carriage, yet Clara got to the storage area with the stasis thing in it, at the end of a carriage?
Are we going to see more of the sonic shoe? Why not use the other shoe to get out?
What an earth was the countdown timer on the screen about. When have we ever had that point of view before. Not to mention Three Lions on his shirt guy sticking his appearance in. Why would he know anything about the inner workings of a Tardis and what was his expertise exactly? The rolls of plans was just crap. Oh and since he lived it's likely Who did save them all - surely he would have kicked off at Clara if Who had left them all to die. Plus when Who found the teleport innards of the mummy, he was intent on using it to recue them to the Tardis. (forcefield be damned) I think we can allow that if there's something Who knows about, it's teleport devices and their use.
Grabbing someone's mind/personality using what exactly? How handy would that have been in previous episodes?
And while we're at it, as someone asked, why was she there at all?
Why the old lady was there was obvious though. She was an expert in dying.
Now for the plot.
So some unknown adversary hi-jacks the Tardis and plonks Who into a new adventure. Clara, in the interim from the last - go screw yourself ending of the episode - has forgiven Who enough that the trot of for one last trip - the boyfriend who won't remember anything of a conversation he had with Clara,** is perfectly fine with it all, despite his previous 'he's going to get you killed' attitude toward Who.
**Because she's going to come back three seconds before she left etc.
then we get an elaborate load of nonsense whereby some people get killed by an apparition only they can see just to convince the captain to let Who deal with something he's been dragged half way across the universe for the sole purpose of investigating.
All those experts - did any of them speak - I can't remember.
Given the rate of attrition, every ten minutes or so, would there have been anyone left to die on the train by the time Who turned up? He got his invite weeks ago.
And so, so entity, knowing Who's abilities, gets him to solve his problem of how the mummy works so he can back engineer it. Marvelous. Four Billion years (estimate) of development and someone who can capture a Tardis, imprison Who and develop a space train with all it's gadgets, can't figure a better way to kill people. Ooh I know, maybe they could capture people (using a teleport device maybe) put them on a space train, buy an alarm clock and shock them all to death with an early morning call. (Or even evacuate the air from their sleeper).
I tell you, whatever these scriptwriters are being paid, it isn't enough. With talent like that they could be making a fortune in Hollywood.
Who's doing this - Who's mother? - why? presumably she can do anything any other time-lord can. She being a time-lord and all. What would be the reason. Did Who leave without tidying his room?
Clara? - She exists in all Who's timeline remember - Could be - Maybe Who's pissed her off so much by the last episode she thinks a little payback is due.
The Master? - Could be - He's done the rounds, maybe this is just another one.
The Queen of hearts? - My personal favourite.
The Cheshire Cat: de-materialisation a speciality - Could be.
God? Dodgy ground. Especially after H982FKL.
Who himself? He's got form for this in the previous episodes - Maybe it's all one big continuance of that.
River Pong? Who did mention her a few weeks back - Could be - Oh please not!!!
Danny? Seems a bit too happy with the Who situation. Could be a setup.
Anyway, basically - Usual poor standard IMO.