When Maisie Williams took on a two-episode guest stint on Series 9 of "Doctor Who," she told BBC America that she enjoyed the "very nice buzz" and "complimentary" nature of the fandom -- until reality set in, and she realized that there was a whole lot of added pressure on a woman of two fandoms to deliver some kick-ass episodes.

MTV News screened said episodes -- "The Girl Who Died" and "The Woman Who Lived" -- ahead of the former's Saturday night (October 17) premiere, and we're officially ready to make a bold statement: Williams is not only the series' best guest actor in years, she's also the lead focus of the two most thrilling and emotionally gratifying installments of the Peter Capaldi era. The girl is just that good.

Here's why dedicating a valuable Saturday night to "Who" -- and specifically, Williams -- is definitely worth your time:

Her character is fifty shades of Season 1 Arya Stark.

... Without her token cynicism, that is.

As much as "Game of Thrones" fans have all loved watching Williams' Arya transform from an innocent tomboy to an arguably sociopathic killer for hire, "Who" affords us the rare opportunity to go back in time and witness an Arya-esque young woman from the days of yore. Williams' character Ashildre is a plucky, effortlessly likable tomboy in a viking village that bares resemblance to pre-Theon Winterfell, and the fact that she only wants to be as loved and respected as the warriors around her is so early-Arya it hurts.

However, that's not saying that "Who" is copying "Thrones" -- far from it. Ashildre's journey from girl to woman is night and day compared to Arya's, and Williams is more than capable of establishing Ashildre as a memorable character in her own right.

Her relationship with the Doctor is genuinely thrilling.

A significant chunk of Williams' two-partner is Companion-Lite, and though we do miss the spirited Jenna Coleman whenever she's not around, it's great to see that Capaldi will be able to shine without her once Coleman departs at the end of this season.

Over the course of two episodes, Williams' Ashildre begins to flow with the Doctor in the same way that Alex Kingston's River Song naturally flowed with Matt Smith's Eleven -- but without any of the clunky backstory that weighed that plot line down. The Doctor's adventure with Ashildre changes things in Twelve's character that should make "Who" fans very, very happy, as they'll almost undoubtedly be good for the show moving forward.

Also, it doesn't take a genius to realize that "Who" has struggled when it comes to defining the Doctor's relationship with Clara (Rose was his conscious, Donna was his best bud, Amy was his family, Martha was a distraction from his grief... but what is Clara?), so it's a relief to see the series write it a companion-esque character who fits with him so effortlessly. We can't really say whether or not Williams will be back -- her "Thrones" schedule should keep her busy for a while -- but it is great to know that this type of chemstriy, in the Capaldi-era, is possible.

She brings world-class Woman Power to "Doctor Who."

We love all of the "Doctor Who" companions for different reasons, but in the Steven Moffat-era especially, the show has taken a lot of heat for fitting its female characters into neat little boxes; and even making some of them into mysteries for the Doctor to solve. Ashildre is a relatably messy, fully-formed character who does help the Doctor realize some issues he's had with himself, but she in no way, shape or form exists solely as an extension of our favorite Time Lord. She has her own wants, and the show never once makes her apologize for that.

She's so confident in who she is and full of Whovian adventure that Clara takes to her straight away, which is nice coming from a show that has never been known for its robust female friendships -- and if the thrill of Robb Stark's real-life girlfriend BFFing around with Arya Stark is lost on you, then why are you even watching "Doctor Who?"