(This article will contain spoilers for Game of Thrones, A Song of Ice and Fire, and George RR Martin’s supplemental material. It will also cover potential plot points that could very well turn up in the future of the series. You’ve been warned!)

Last week on Game of Thrones, we were teased by the “Tower of Joy” sequence and unceremoniously yanked out of Bran’s vision before we could enter the tower with Ned Stark. For casual viewers, this was just a cool fight scene with a hint of mystery, but to those who have been reading and theorizing about A Song of Ice and Fire for years, it was a somewhat irritating stalling tactic for a reveal that we’ve been expecting for a long time. The R+L=J theory is so well-known and well-supported at this point that it’s essentially canon, so holding out of the reveal feels less like suspense and more like prolonging the inevitable.

But there’s another theory that is less widely accepted by fandom and, I feel, almost as likely to be true as R+L=J. If you’re paying close attention to the supplemental material and the scenes included in the TV adaptation, there’s a strong reason to believe that Tyrion Lannister is, himself, half-Targaryen.

When the theory was first proposed, it was largely based on dialogue from Tywin Lannister and a few lines about Aerys Targaryen’s interest in Tywin’s wife Joanna. I’ll start with these, because they’re the most easily debunked. There are a number of points in the story when Tywin tells Tyrion that “you’re no son of mine,” or that he can’t prove that Tyrion isn’t his son. Of course, by themselves, this doesn’t mean much; Tyrion and Tywin have a very antagonistic relationship, and Tywin would love to distance himself from the “monstrosity” that is his son.

But the supplemental coffee table book, The World of Ice and Fire, heavily complicates things. In its history of the Targaryen dynasty, the chapter on Aerys Targaryen, the “Mad King,” reveals that Tywin and Aerys were once very good friends, but eventually a rift formed between the two that led to the Lannisters’ betrayal during Robert’s Rebellion.

Aerys was infamous for his whoring and adultery. His wife repeatedly dismissed handmaidens from their service because of Aerys’s predilections towards them, one of which was Joanna, Tywin’s future wife. Flashing forward a bit, after the birth of Rhaegar Targaryen, Aerys and his wife were unable to birth a healthy baby. Their attempts ended in still-births of deformed children. Meanwhile, Tywin and Joanna gave birth to Jaime and Cersei, two healthy, beautiful children. Aerys blamed his wife for the troubles, suggesting that he “married the wrong woman.”

Eventually, Aerys calls Tywin and his family back to court, and lo and behold, less than a year later, Joanna dies giving birth to Tyrion Lannister. Baby Tyrion was described and regarded as hideous, a deformed monstrosity with an enormous head, demonic eyes, and a tail. These descriptors match up quite well with those of Aerys’ attempted children with his wife.

It’s not hard to see what I’m suggesting here: Aerys Targaryen was the one to blame for his malformed children, and he had sex with (and possibly raped) Joanna Lannister, leading to the birth of Tyrion Lannister. While this somewhat undercuts the drama between Tywin and Tyrion, as Tywin would not be Tyrion’s father, it also helps explain Tywin’s hatred for Tyrion. He can’t prove anything, but he doesn’t believe Tyrion to be his son. He sees him as a long, cruel offense on his family by his former-friend Aerys Targaryen. Aerys’ misdeeds killed Tywin’s wife and forced him to raise a constant reminder of his own loss.

Of course, even with all of that supporting evidence, the Tyrion Targaryen theory isn’t as strong as R+L=J. The latter theory actually clarifies elements of the story, such as Ned’s honor, that are questionable before its reveal. However, I do think that there have been some interesting decisions in the HBO series adaptation that further suggest that the theory is true.

The most damning, in my eyes, is the inclusion of the Stone Men boat attack in season 5. In the books, Tyrion hitches a ride down the Rhoyne River on a boat with the Griffs and their crew on his way to meet Daenerys Targaryen. Partway through, they get attacked by Stone Men, who suffer from greyscale, an incredibly contagious and ultimately lethal disease. During the attack, Tyrion gets grabbed and pulled underwater by one of the men and is apparently fine. Meanwhile, “Griff” (aka Jon Connington) barely touches one of the assailants and is afflicted with greyscale.

In the series, there is no trip down the Rhoyne, nor do any of the characters in the scene (aside from Tyrion) appear in the story. However, there is still an attack on Tyrion by the Stone Men. In this scene, Jorah has kidnapped Tyrion and both of them get attacked just outside of the ruins of Valyria. Similarly to the books, Tyrion gets dragged underwater by one of the Stone Men and is just fine, while Jorah contracts greyscale after barely touching one of them.

It’s notable that the show went to great lengths to make sure that this scene was included. They not only shoehorned it in during a different point of the narrative with a different character accompanying Tyrion, but they actually changed the lore of the series in order to make it viable. in the books, the Stone Men haunt the Rhoyne river, and it is rumored that their presence was caused by a curse inflicted on the area after the Valyrians wiped out their civilization. In the series, though, the Stone Men inhabit Valyria itself, NOT the Rhoyne River. While the series frequently makes changes to the way that events play out, this is the only outright contradiction to the lore, as far as I can tell.

The question is, if you’re adapting the books and dropping just about every element of Tyrion’s book-five story, why include that one scene? Why go to such great lengths when the person afflicted by greyscale is apparently flexible? To get to the bottom of it, let’s look at what IS the same in each version: Tyrion is directly exposed to the Stone Men and unaffected, while another character will suffer from the tiniest contact with them.

The show mentions it less than the books, but the Targaryens are immune to almost all disease. Right around the time that Tyrion is having his run-ins with Stone Men in the book, Daenerys is watching much of Meereen suffer from a plague. While her court has to be extremely careful not to contract the illness, Daenerys’s heritage keeps her completely safe.

It is my belief that David Benioff and D.B. Weiss jumped through hoops to include the Stone Men scene specifically to foreshadow that Tyrion is a Targaryen, and therefore immune to disease. I think this goes even further this year, with Tyrion’s scene with the dragons. Part of this is shared in the books, as well; Tyrion’s monologue about being fascinated by dragons as a kid is lifted almost verbatim from descriptions in the book, lending further credence to his Targaryen bloodline. Tyrion tries to explain that they won’t harm him because they’re smart and can tell friend from foe, but the fact that they were known to kill innocents and slave-owners in previous seasons suggests otherwise. It seems more plausible that Tyrion is spared because the dragons can sense his bloodline.

Finally, there’s the idea of the “three headed dragon.” When Aegon Targaryen conquered Westeros, it was with his two sister-wives, each of whom had their own dragon. This is why the Targaryen sigil is the three headed dragon; each head represents a different conqueror. There have been a number of suggestions, especially within the book, that Daenerys’s conquest would also involve a “three headed dragon.” It seems that the second head is almost definitely Jon Snow, but that still leaves a third, and who is likely to fill that position?

In the books, there’s still the possibility that it’s Rhaegar’s son Aegon Targaryen, whose death was allegedly faked in order to facilitate a future coup. But given that the TV series has chosen not to adapt this storyline at all, Tyrion is a much stronger candidate. His story has already become entangled with Daenerys’s, and there’s plenty of evidence to believe that he is part of the bloodline.

This theory is obviously not fool-proof. It relies on a bit of supplemental reading, as well as off-handed asides and meta-textual analyses of both the book and the show. But just looking at what’s laid out and how storytelling typically works, it makes a lot of sense. I’m not a gambling man, but I’d be willing to put money on this one.