"Game of Thrones" fans think they've solved the mystery behind the coffee cup that was accidentally left behind during Sunday night's episode.

[WARNING: The following contains spoilers from "Game of Thrones"]

The cup, which was first spotted by a Reddit user, appears during a scene from Season 8, Episode 4, while Jon Snow and Tormund Giantsbane celebrate the victory over the Night King.

The camera pans to Daenerys Targaryen, who is sipping wine when an object from out of the realm appears sitting on the table: a disposable coffee cup that was left while the scene was being prepped.

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Despite HBO issuing an apology admitting the cup "was a mistake," fans took to Reddit again, this time to point the blame towards Sophie Turner.

An eagle-eyed fan noted that Turner, who plays Sansa Stark in the fantasy series, was seen in a photo on social media holding the same brand of coffee cup that appeared in Sunday night's episode.

“Starbucks cup mystery solved. Sansa is petty, the north remembers,” one person posted on Reddit alongside the photo, as first reported by the New York Post.

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"[That feeling when] you purposely leave your coffee in front of Dany knowing she’ll get all the blame,” a user posted in reference to the tension between Sansa and Daenerys.

A rep for Turner did not return Fox News' request for comment.

HBO confirmed to us on Tuesday that the cup had been digitally removed from the episode.