Sunday night’s Game of Thrones had hours of essential information, major narrative developments, and character reunions all packed into one swift episode. We could spend forever analyzing – SPOILER alert – Cersei’s pregnancy reveal, how long Gendry will stick around, and what Gilly’s major Rhaegar Targaryen bomb drop reveals about Jon’s threat to Daenerys’ right to the throne. But one of the more unexpected and interesting developments in “Eastwatch“ was the raven Arya discovered in Littlefinger’s room. What did it say? Is Littlefinger tricking Arya? And what does that mean for the two Stark sisters?

First, let’s take a closer look at the letter:

HBO

You may have thought this was a fake letter Littlefinger planted, but it’s 100 percent real. It’s the letter Sansa sent to her brother Robb back in Season 1 Episode 8. Here’s the letter in full:

Robb, I write to you with a heavy heart. Our good king Robert is dead, killed from wounds he took in a boar hunt. Father has been charged with treason. He conspired with Robert’s brothers against my beloved Joffrey and tried to steal his throne. The Lannisters are treating me very well and provide me with every comfort. I beg you: come to King’s Landing, swear fealty to King Joffrey and prevent any strife between the great houses of Lannister and Stark.

Your faithful sister, Sansa

It’s important to remember that Sansa wrote this letter under duress, when Cersei (along with Pycelle, Littlefinger, and Varys) manipulated her into writing it. Back in Season 1 Sansa was still innocent and malleable, still eager to marry Joffrey and not yet hardened by the tragedies that came later.

When Rob eventually received the letter, Maester Luwin told him that it may have been written by his sister, but it was clearly with Cersei’s words. But the problem is this: Arya doesn’t have that context, and she’ll be led to believe her sister played a part in their father’s death.

For the past several weeks Littlefinger has seemed more off his game than usual, caught by surprise by the return of two Starks, including one who saw right through him. I’ve been wondering for weeks what Littlefinger’s endgame is, and “Eastwatch” finally made that clear: Pitting the Stark sisters against one another so Littlefinger has more control over Sansa. With Arya in the way, Littlefinger can’t have control over Sansa. Arya’s been on to him, but he’s on to her, so planting the scroll in his bedroom is the quickest way to get Arya to turn on her older sister, who’s grown to reflect Cersei more (that hairstyle) as Arya’s come to resemble her father. As D.B. Weiss explains in the “Inside the Episode” following “Eastwatch,” all Littlefinger needs now is to “give Arya a cause to display real rage towards Sansa.”

The preview for Episode 6 teased a tense standoff between Arya and Sansa. Will Arya be coerced into killing her sister? The catspaw’s dagger was already used in an attempt to kill one Stark, so it could play a role in another Stark assassination attempt. But that seems too drastic (or too tragic and heartbreaking) to believe. Littlefinger is likely just trying to cause a rift between the two so Sansa turns to him for counsel. Still, something drastic is bound to happen; it’s the penultimate episode of the season after all, and the show won’t be cutting between Winterfell and the sure-to-be-insane battle at Eastwatch for nothing. Will the sisters see through this scheme and both turn on Littlefinger? Someone is gonna die, and I’ll be in a perpetual state of anxiety for the next six days until we find out.