Warning: spoilers for Game of Thrones below!
While watching Game of Thrones season seven's sixth episode, you might have found it kind of hard to focus on anything other than Jon Snow's White Walker battle happening beyond the wall (zombie dragons are huge attention hogs, you know?). But while all of that is certainly interesting, an important subplot involving Sansa, Arya, and Littlefinger has been brewing down at Winterfell. It might seem a little confusing, what with all the backstabbing and subtle political machinations, but if the most recent episode is any indication, the question of who will end up killing Littlefinger might have finally found an immensely satisfying answer.
It has long been suspected that Arya will be the one to take out the former Master of Coin, but a new theory has emerged courtesy of Reddit user banohal suggesting that it will actually be Sansa who ends Littlefinger's manipulations once and for all. The reasoning behind the idea that Sansa will take over for Arya as Littlefinger's murderer all comes down to that Valyrian steel dagger, also known as the "catspaw" blade.
Back in season one, an assassin is sent to Winterfell to kill a comatose Bran Stark with the dagger in his own bed. Luckily his mother, Catelyn Stark, intercepts the assassination attempt and fights off the attacker with her bare hands. This is actually what sets off the rift between the Starks and the Lannisters, since Lord Petyr "Littlefinger" Baelish tells Catelyn that the catspaw blade belongs to Tyrion Lannister (who actually lost it in a bet and has nothing to do with hiring the assassin). Catelyn then takes Tyrion hostage as payback without realizing he's not the one behind it all, setting off the events that lead to the War of the Five Kings. In short, although Littlefinger doesn't hire the assassin to kill Bran (that we know of), he does manipulate Catelyn into starting a bunch of drama because he knows he can use it to his advantage. If one of the Stark siblings ends up taking him out, it would be sweet, sweet justice.
That's what brings us back to the latest theory. In season seven's fourth episode, "The Spoils of War," Littlefinger gives Bran the very same Valyrian steel dagger that was meant to kill him all those years ago, to presumably curry favor with the young Stark. After Bran responds cryptically, he gives Arya the blade a few scenes later when she makes her grand return to Winterfell. In the season's sixth episode, Arya hands off the dagger to Sansa during a tense conversation. Where might it go next? Banohal's theory suggests Sansa will find the perfect spot for it: Littlefinger's throat. They wrote:
Littlefinger gives the dagger to Bran as part of an attempt to gain favor.
Bran does not want it and gives it to Arya. This symbolizes the first Stark rejecting littlefinger.
Arya gives it to Sansa. This represents the second Stark rejecting Littlefinger.
To come full circle, Sansa needs to give it to Littlefinger. Right to his throat. And the final Stark will have rejected him for good.
Another layer to consider is that Sansa so clearly idolizes her late mother, Catelyn, who also rejected Littlefinger time and time again before her death. Littlefinger, blinded by his thirst for power and desire to control/own Sansa, would essentially fall into his own trap.