Here's what was in that scroll Littlefinger wanted Arya to find — and what it says about his master plan

Lord Petyr "Littlefinger" Baelish put part of his mysterious master plan into work on Sunday's episode of "Game of Thrones."

In a scene late in the episode, Arya follows Littlefinger to his room at Winterfell, where he receives a mysterious scroll from an unknown man. Littlefinger asks the man delivering the scroll if it is the last remaining copy in Winterfell, and is told that it is. After Littlefinger leaves his room, Arya enters and searches for the scroll. Arya finds the scroll and seems to be shocked by its contents.

The scroll is from the first season of "Game of Thrones," when Cersei tells Sansa that the only way she would spare the life of her father (Ned Stark) is if Sansa writes to her mother (Catelyn Stark) and brother (Robb Stark), and asks them to bend the knee to Joffrey. Of course, Ned Stark is executed in season one, but not before Sansa sends ravens to her mother and brother, doing as Cersei and her advisors at the time (one of whom was Littlefinger) instructed.

The scroll that Arya finds is the scroll that Sansa sent to Robb.

This is what the scroll says:

"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."

In Sunday's episode, Littlefinger watches Arya leave his room, smirking — clearly he intended to lead Arya to find the scroll. Littlefinger is trying to sow seeds of doubt between the sisters. After all, what could upset Arya more than finding a letter from Sansa asking Robb to bend the knee to the person highest on her kill list?

Earlier in the episode, Arya questions Sansa's motives for hearing out the houses allied with Winterfell, who criticize Jon Snow for meeting with Daenerys. Arya accuses Sansa of preparing for leadership, should Jon not return to Winterfell, insisting that Sansa secretly wants to rule.

Sansa is surprised and uncomfortable with Arya's accusations, and quickly dismisses them before exclaiming that she needs to return to work. The Stark sisters have only just united and are already skeptical of one another. Littlefinger can see this and is choosing to exploit it by having Arya find that scroll.

On “Game of Thrones: Inside the Episode,” showrunner D.B. Weiss explained the motivation behind Littlefinger’s desire to drive a wedge between Arya and Sansa.

Weiss said:

“Arya is very used to being more clever and more stealthy, and smarter than any of the people she’s up against, but she hasn’t dealt with Littlefinger for a while. She gets roped into spying on somebody who's actually leading her by the nose to something that he wants her to have.

He’s looking for a way to prevent this sister bond from developing further because the tighter they are the more definitively he is caught on the outside of it. On the Sansa end of the relationship he’s seen the opening and now all he needs to do is give Arya a cause to display real rage towards Sansa. And, he knows full well that with what’s going on in Sansa’s head with regards to Arya and how dangerous she is, when Arya starts to act dangerous, and act angry, he knows where Sansa is going to turn.”

By actively working to keep the Stark sisters from forming a tight-knit bond, Littlefinger can remain Sansa's confidant. And thus Littlefinger is one step closer to being Sansa's sole counsel, and just a little more powerful.