Doctor Who fans found last week's episode of the series surprising, especially with the big reveal about Ashildr, the character played by Game of Thrones' Maisie Williams.

The upcoming episode, though, will tell us more about that character as the second part of a two-part story, and it looks like Ashildr has been busy since she last saw the Doctor (Peter Capaldi).

In "The Woman Who Lived," The Doctor arrives to find himself in 17th century England. A sneak peek of the episode shows the TARDIS landing. Out pops the Doctor who uses a strange new gadget to detect something that he's looking for (probably because his sonic screwdriver is gone and his sonic sunglasses got destroyed).

This clip also shows the Knightmare, a villain who robs a carriage. However, that bandit looks a lot like Ashildr, so it seems that she's been up to no good since the Doctor last saw her.

Of course, the Knightmare has something otherworldly on her side, as seen in the sneak peek. Just what is Ashildr after? And what will her reunion with The Doctor be like?

Here's the official synopsis for "The Woman Who Lived":

"England, 1651. Deadly highwayman 'the Knightmare' and his sidekick stalk the dark streets of London. But when they find loot that is not of this world, they come face to face with the Doctor. Who is the Knightmare in league with? And can the Doctor avoid the hangman's noose and protect the Earth from a devilish betrayal?"

This clip also shows something else: the absence of the Doctor's companion, Clara (Jenna-Louise Coleman). The BBC already reported that Coleman plans on leaving the series this season, so does something happen to her in this episode? Does Ashildr become the new companion? After all, Williams recently expressed interest in returning to the series as the character and even teased that this isn't the last time fans will see her on the show.

"I hope that she comes back, everybody's been asking if she comes back," said Williams to Metro. "I know they've had characters similar to Ashildr that have returned in future episodes and series, so we'll see. I think there's a good chance!"

Of course, it makes sense that an immortal, such as Ashildr, share the TARDIS with the Doctor, who is also immortal in his own way, especially considering how much the Doctor has complained recently about always losing his friends. However, it's likely that Williams is too busy with her role as Arya Stark on Game of Thrones to take on a full-time role on the BBC series.

Doctor Who airs on BBC America on Saturdays.

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