Even though it seems like Game of Thrones is just getting started, this season is still almost halfway over, with the airing of tonight's episode Book of the Stranger. Following tonight's epic episode, HBO has debuted a new preview for next week's episode, The Door, which marks the halfway point of the season when it airs one week from today, Sunday, May 22 at 9 PM ET on HBO. Be warned, if you haven't watched tonight's episode of Game of Thrones, there will be SPOILERS below, so read on at your own risk.

The trailer opens with a reunion many fans had been waiting for, with Sansa Stark (Sophie Turner) confronting Petyr "Littlefinger" Baelish (Aidan Gillen), asking him if she knew about how treacherous and dangerous her former husband Ramsay Bolton (Iwan Rheon) really is. Shortly after Sansa was married to Ramsey, he brutally raped her while forcing Theon Greyjoy (Alfie Allen) to watch in one of the show's most controversial episodes to date. In the Season 5 finale, both Sansa and Theon managed to escape Winterfell, and this season they both got some much needed assistance from Brienne of Tarth (Gwendoline Christie) and Podrick (Daniel Portman).

RELATED: Eternals Won't Feature Black Knight, But Does Have a Game of Thrones Reunion

Tonight's episode showed another reunion, with Sansa, Brienne and Podrick making it to Castle Black to find Jon Snow (Kit Harington). Sansa revealed that she wants to fight and reclaim Winterfell from the Bolton's, with the help of Jon Snow and an army of Wildlings. This preview for The Door doesn't reveal anything about Sansa and Jon's plans to overtake Winterfell, but we do get another glimpse of Sansa's sister Arya (Maisie Williams) and her mentor Jaquen H'gar (Tom Wlaschiha), along with a glimpse of the Kingsmoot on the Iron Islands, which was mentioned in tonight's episode.

Towards the end of Book of the Shadow, Theon finally returned home to the Iron Isands, where he told his sister Yara (Gemma Whelan) that he wants to help her rule the Iron Islands, after their father was killed. The Kingsmoot ceremony is held to determine who will be the new ruler, with this footage showing Yara claiming the throne, but we don't see anyone else step up quite yet. It's quite likely that she will be challenged by Euron Greyjoy, Yara and Theon's uncle, who killed their father earlier this season. We also meet a new and mysterious character, who, judging by the elaborate necklace she's wearing, is another red priestess like Melisandre (Carice Van Houten), who offers counsel to Tyrion Lannister (Peter Dinklage) and Lord Varys (Conleth Hill).

The final scene of the trailer is quite intriguing, showing Bran Stark (Isaac Hempstead-Wright) having another one of his greensight visions, where he meets thousands of undead soldiers before turning around to see none other than the Night's King. Since greensight allows Bran to see the past, present and future, we don't know for sure when exactly this "vision" takes place, but we'll find out more when The Door airs one week from tonight. We also have three new vidoes that go behind-the-scenes of Book of the Shadow, which you can check out below.