If "Kill the Moon" wasn't dark enough for some Doctor Who fans, "Mummy on the Orient Express" will give viewers another dose of sci-fi horror.

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Twelve (Peter Capaldi) won't be the problem this time, however, and a proper monster will fill the role of antagonist in episode 8 of season 8.

The thing about the title 'Mummy On the Orient Express' is, you think it's going to be a silly romp, and it's so not," teased writer Jamie Mathieson, according to Blogtor Who. "From the first death onwards, you're like, 'Oh, this is quite dark.'"

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Traveling on the galactic version of Earth's Orient Express, the Doctor and Clara (Jenna Louise Coleman) must rush to save the passengers from a rather homicidal mummy. Victims only have 66 second of life left once they lay eyes on the deadly creature, and our intrepid time travelers will have to suss out the baddie before it is too late.

Unfortunately for Clara and the Doctor, this particular mummy won't look like a reanimated King Tut.

"The issue I had in constructing the plot was, how do I hide the Mummy?" explained Mathieson explained, according to Blogtor Who. "I thought, 'As soon as the Mummy starts killing people, how stupid are the passengers - and the Doctor - if they can't spot the killer? I had all sorts of ideas until eventually I came up with the final solution... which I think is a bit spoilery to reveal here!"

Find out more when Doctor Who airs Saturdays on the BBC and BBC America. Scroll through the photos above and click the video below to see what's in store for Clara and the Doctor in "Mummy on the Orient Express."