It's all happening, you guys.

After years of speculation, Game of Thrones is finally poised to reveal the truth about Jon Snow's (Kit Harington) parents. To many fans' delight, the "Oathbreaker" trailer clearly shows Bran (Isaac Hempstead-Wright) having a vision that takes place at the legendary Tower of Joy.

If that name means nothing to you, don't worry. The Tower of Joy hasn't been mentioned on the series, but it is the focus of a crucial book sequence tied to the popular R+L=J theory, which hints that Jon Snow is actually the son of Ned's (Sean Bean) sister Lyanna Stark and Daenerys' (Emilia Clarke) brother Rhaegar Targaryen.

Everything you need to know about Rhaegar Targaryen

Depending on who you ask, Lyanna was either abducted by Rhaegar or ran off with him willingly when Ned was still a young man. No matter the motivation, it was Lyanna's disappearance that caused her fiancé, Robert Baratheon (Mark Addy), to begin his rebellion against the Targaryens.

At the very tail end of the war, Ned led a group of six men, including Meera Reed's (Ellie Kendrick) father Howland, to rescue Lyanna from the Tower of Joy in Dorne. However, Lyanna was being guarded by three Kingsguards, including one of Rhaegar's good friends and the legendary knight, Ser Arthur Dayne. Only Ned and Howland managed to survive the ensuing battle, but when they finally made it inside the tower, Ned discovered Lyanna in a "bed of blood." But before Lyanna died, she entrusted Ned with a top-secret promise.

Was the promise simply to keep her newborn son, Jon, safe from Robert Baratheon? Or is there more to it? We break down the three most likely things that went down at the Tower of Joy in the video above.

What do you think happened?

Game of Thrones airs Sundays at 9/8c on HBO.