The Door (Season 6, Episode 5)

"The Door" is the fifth episode of the sixth season of HBO's fantasy television series Game of Thrones, and the 55th overall. The episode was written by series co-creators David Benioff and D. B. Weiss, and directed by Jack Bender.

Bran Stark learns the origin of the White Walkers, Jon Snow plans to unite the north against the Boltons, Euron Greyjoy reveals his return to the Iron Islands at the Kingsmoot, Tyrion Lannister meets with the Red Priestess Kinvara, and Daenerys Targaryen sees the depths of Jorah Mormont's devotion to her.

https://en.wikipedia.org/wiki/The_Door_(Game_of_Thrones)