A Heart of Stone

A Heart of Stone is the eight episode of Season 6 of Game of Thrones.

Plot
Sansa is wed.

At Harrenhal
The wedding of Sansa Stark to Harry the Heir is set to occur.

Jaime Lannister arrives, and a suspicious Littlefinger allows him and his "bodyguard" Brienne inside the castle.

Tom O'Seven-streams begins to play the Rains of Castamere while other disguised Brotherhood members take positions around the Freys. Confusion sets in when Black Walder stabs Lame Lothar, claiming that the Rains of Castamere were a signal for Lothar to kill Black Walder and eliminate him from the line of succession. Crossbowmen begin firing, and Jaime and Brienne realize they are loyal to Black Walder. Littlefinger silently ducks out of the area when his own guard arrive and begin murdering Freys. The Brotherhood themselves begin slaughtering Freys, and a massive battle opens in the dining hall.

Catelyn and her men arrive and begin the search for Sansa. Littlefinger orders Lyn Corbray to prevent anyone from leaving the castle, and capture Jaime. Jaime tells Catelyn that Sansa is in the bedding chambers. Lyn confronts Jaime, and a duel begins between the two and Brienne, distracting Lyn and allowing Catelyn to continue her search.

Catelyn arrives in the bedding room. Sansa sees Lady Stoneheart realizes that she's her mother. Catelyn is suddenly stabbed by Black Walder, who grunts about having to kill her twice. Black Walder moves to kill Sansa, but Sansa smashes a goblet into his face then slashes his throat, killing him. Sansa then cradles Catelyn in her dying moments. Catelyn states she has always been proud of Sansa before she dies again. Sansa cries holding Catelyn's body when Littlefinger and his men arrive in the room. Littlefinger looks in horror at the body, and then orders his men to escort Sansa to safety out of Harrenhal.