By Brandi Fowler
Updated Aug 21, 2017 @ 6:45 pm

It appears things are not as they seemed when it comes to Arya and Sansa.

While there were hugs and smiles when the Stark sisters first reunited on Game of Thrones after years of separation (during which Sansa thought Arya was dead), things got beyond tense in last night's "Beyond the Wall," the sixth episode of Season 7. In it, Maisie Williams's Arya directed serious anger—that tiptoed the line between passive-aggressive and aggressive-aggressive—at her older sibling.

In the previous episode, Arya found a letter, planted by the ever-manipulative Littlefinger, that Sansa (Sophie Turner) had written back in Season 1 to her older brother Robb. The note praises the Lannisters and claims her father, Ned Stark, tried to steal the Iron Throne from King Joffrey. But during Sunday's episode when Sansa explained to Arya that Cersei had forced her to write the words (something Robb's advisers immediately recognized), Arya would hear none of it. The youngest Stark sister continued to blast her big sister, saying that she betrayed their entire family for her "beloved Joffrey" in exchange for power and pretty dresses who actually tortured Sansa after she was forced to marry him.

Sansa Arya - Game of Thrones
Credit: Helen Sloan/HBO

The argument culminated when Arya walked slowly towards Sansa with her Valyrian steel dagger—suggesting that she might use her Faceless Man tricks to literally take her place. Instead, Arya turned the knife away from her and slipped away.

Post-episode, fan conspiracy theories and blog posts popped up, with headlines like "Is Arya Going to Kill Sansa?" Fans are also wondering whether Sansa will kill Arya—after all, right after Littlefinger suggests that she keep Brienne of Tarth around for protection from her little sister, Lady of Winterfell sends her off to King's Landing. Alternative theories: Arya has already killed Littlefinger and is wearing his face or Arya is simply pretending to fall into Littlefinger's trap and planning to team up with Sansa to take him down together.

VIDEO: Game of Thrones: Sophie Turner Explains that Sibling Rivalry

But what's really going on with these two? According to Entertainment Weekly, it's a major part of Littlefinger's plan to pit them against each other and convince Sansa to get rid of Arya for good.

Co-executive producer Bryan Cogman told the mag, "Sansa and Arya are characters who were never close and never particularly liked each other and have been through so much. Now they have more in common than either are probably willing to recognize." He continued, "Just because the Starks have reunited doesn't mean it's going to be sunshine and roses."

Meanwhile Turner, who plays Sansa, also gave her take, adding, "In the books, it says something about how Arya and Sansa are different sides of the same coin. They love each other but they're so different. They never really got along. And now that they're back together that's heightened because they've gone down totally different paths and have had to adapt to totally different situations to the point where they don't see on each other's level."

"They don't really talk about what they've gone through. They never really had that communication before, and now when it's vital to do they don't have that and can't understand each other," she says. "Arya still sees Sansa as a snooty prissy child that she was before she left for King's Landing. There's a big lack of communication. There's this underlying tension. It's like a f—ing horror movie."

As for what will become of the two ... we'll have to wait and see. As we've seen, anything can happen on Game of Thrones.