As soon as the "Game of Thrones" season 7 first trailer has been released, a lot of fans noticed a very important detail: the fight between Jon Snow and Littlefinger takes place in the Winterfell's crypt. In the "GOT" season 7 episode 2 promo video, we can see Yohn Royce, a powerful bannerman of House Arryn, telling Jon that "a Targaryen cannot be trusted." The video also features a brief but delightful scene of Jon choking Littlefinger.

This can only mean one thing: Jon Snow's true heritage is going to be revealed in the next episode of the show.

Who is going to tell Jon the truth about his parents?

Considering where the fight between Jon and Littlefinger takes place, we have no doubt: Lord Petyr Baelish, the most skilled manipulator in the Seven Kingdoms, is the man who will reveal Jon that he's not Eddard Stark's son. As we all know, Jon is the son of Lyanna Stark and Prince Rhaegar Targaryen.

As you can see from the video below, Jon is not going to react well to Littlefinger's reveal.

If you want to watch the other scenes featuring Jon and Littlefinger in the Winterfell's crypt, you can also rewatch the first "Game of Thrones" season 7 trailer.

What is Littlefinger planning?

Why Petyr Baelish decides to tells Jon about his heritage?

This is a very good question. Littlefinger has no power over Jon Snow; his hope is to put Sansa in charge of Winterfell so he can do some new creepy mind-games with her. Yohn Royce's words, "a Targaryen cannot be trusted," may be referred to Daenerys Targaryen, but we cannot exclude that Royce's is publicly undermining Jon's authority with his statement.

Anyway, what's important here is the fact that if Jon is not Eddard's son and is half Targaryen, his authority is undermined. Sansa may even use this information to support her claim as "Queen of the North." Although we don't know precisely what is going to happen between Jon and Sansa, Littlefinger's move is going to be a smart one from his point of view.

The information he is going to disclose is going to shake up things in the north, and we should never forget what Petyr Baelish told Varys in the third season of the show: "Chaos is a ladder. Many who try to climb it fail and never get to try again. The fall breaks them. And some, are given a chance to climb. [...] The climb is all there is."

"Game of Thrones" season 7 episode 2 will air on Sunday, July 23, on HBO. The next episode's title is "Stormborn."