WARNING: Major Spoilers ahead for the seventh season of Game of Thrones! Read ahead at your own risk...

The latest episode of Game of Thrones was jam-packed with moments that made audiences leap from their seats, but there's a possibility we may have missed the biggest reveal of all.

Some fans online have noticed a mysterious woman lurking around Winterfell; a woman that looks a lot like the late Catelyn Stark.

One of the most talked-about scenes in the episode saw Arya prove her fighting skills by sparring with Brienne. While everyone was caught up in their duel, no one seemed to pick up on the woman in the background.

Watch the scene (above) one more time. While the two characters are chatting, a woman walks by. This woman has auburn hair, and is wearing an elegant green dress. Both features were trademarks of Lady Catelyn. Who else in Winterfell would have the money for a dress like that?

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While you could argue that this is just a random woman walking through the town, let's look at how she's moving. This figure walks past the door behind Arya at around the 12-second mark. She walking briskly, with her head down, from the right side of the screen to the left.

Now, Arya and Brienne spar a bit, and the woman reappears right around 1:00 into the clip. If you watched the fight carefully, Arya and Brienne traded positions twice, putting the youngest Stark back where she began. When the woman turns up the second time, she's walking the exact same way, going in the exact same direction.

There's no way this woman walked all the way around that large courtyard in just 47 seconds. She wasn't a medieval mall-walker.

So, this was either a mistake made by whoever was coordinating the extras, or this was a purposeful inclusion by the creative team. As you probably know, Game of Thrones doesn't make those kinds of mistakes very often.

Catelyn has been dead for a while, but her return as a ghost wouldn't exactly be out of the ordinary. Throughout Game of Thrones, plenty of characters have come back from the dead. Jon Snow, the White Walkers, the Lord of Light - death means nothing in this world. Catelyn could easily be back in Winterfell, watching over her recently-reunited family.

Fans of the books have been pulling for a Catelyn return for some time now, since George R.R. Martin found a way to give her a second life in the source material. In that version, Catelyn was brought back as an undead killing machine, known as Lady Stoneheart.

This possible ghost isn't what fans would have been expecting from Catelyn's return, but it's definitely something to cheer about. Let's just hope this was a purposeful inclusion, not a random mistake.