Before we get into any of this, if you’re not caught up on HBO's Game of Thrones, we’re about to unleash a whole lot of spoilers. (Same goes for all of the published books.) So if you haven’t finished watching the sixth season, go do that now. Then come back.

By now, even the most casual Game of Thrones watchers know that when there are still a few months to kill before the new season premieres (in this case, season seven on July 16), any hint at what the next episodes will bring is enough to get the creative wheels turning in a serious fan’s head. Which is why, at various times over the years, we’ve reported on several fan theories—some of them plausible, some of them kookier than Lady Lysa Arryn.

One of the theories that has long been debated by viewers revolves around a vision that Daenerys has in George R.R. Martin's book series, A Song of Fire and Ice. The vision is of her brother, Rhaegar Targaryen, who talks about his son as “the prince that was promised.” In the vision, Rhaegar also says "there must be one more ... the dragon has three heads." As Nerdist reports, “it has long been assumed that in order to ride a dragon—and in turn be one of the three heads to ride Dany’s kiddies into the future to save Westeros from the White Walkers—one must have Targaryen blood.”

We got one step closer to figuring out who this dragon-riding trio might be when it was revealed in season six that Jon Snow, the supposed bastard son of Ned Stark, is actually the son of Lyanna Stark (Ned's sister) and Rhaegar, which makes him Daenerys's nephew. Rather than bask in the joy of finally knowing for sure who Jon’s parents were, fans immediately began wondering about that third head—and how it might play into another popular fan theory that asserts that Tyrion Lannister is not a Lannister at all, but the product of an affair between Joanna Lannister and Aerys II Targaryen (a.k.a. the Mad King).

This is where we get to the new theory we promised: Over at Mashable, Alex Hazlett has laid out an extremely detailed—and very believable—idea that it’s that Kingslayer Jaime Lannister who, in fact, has the Targaryen blood and is being set up to become the show’s true hero. To understand the nuances of Hazlett’s theory, you’ll want to read her piece in full. But if you go in a skeptic, be forewarned that she has photographic proof … well, sort of.

The picture above, one of the promotional images for season seven, is what sparked the theory because of one tiny detail: that shiny sword. Remember that prince that was promised? Well, he’ll carry a burning sword known as Lightbringer with him, and he’ll use it to wreak all sorts of havoc before he can begin on his path to redemption. (Nerdist breaks that all down here.)

It’s an intriguing theory, to be sure, and one that would open the door to a variety of surprising—and bloody—storylines. (Hey, it’s Game of Thrones.) For now, we’ll all just have to wait and wonder.