Maisie Williams Is Super Mysterious In 'Doctor Who' Season 9 Trailer

Maisie Williams may have struggled to become "no one" in Season 5 of "Game of Thrones," but in "Doctor Who" she is definitely someone, and someone important.

The first trailer for Season 9 of "Doctor Who" debuted at Comic-Con on Thursday. After an action-packed look at what's to come -- including a look at Peter Capaldi's Doctor rocking out on a guitar -- the last moments of the trailer reveal Williams' new character. "You," the Doctor says to her in surprise. "What took you so long, old man?" Williams quips back.

Who is "you"?! We're not sure, but we do know Williams' character is expected to "give [the Doctor] exactly the right sort of hell," according to executive producer Steven Moffat. So it's Arya Stark in a different dimension. Count us in.

Season 9 of "Doctor Who" premieres Sept. 19 on BBC America.

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