One of the biggest 'House of the Dragon' book changes may have introduced a major plot hole to the show

• Addam of Hull becomes the dragon Seasmoke's new rider in "House of the Dragon" season two.
• This shouldn't be possible because, last we heard, Seasmoke's rider Laenor Velaryon is alive.

Warning: Spoilers ahead for "House of the Dragon" season two, episode six.

"House of the Dragon" hasn't been shy about taking some liberties with its source material. But one of those changes has led to major confusion among some fans.

The HBO hit, based on the fictional House Targaryen history book "Fire and Blood" by George R.R. Martin, the author of "Game of Thrones," made its biggest departure from the book so far back in season one when it changed the fate of Laenor Velaryon.

Laenor was Rhaenyra Targaryen's first husband. In the book, Laenor is killed by Ser Qarl Correy, who is described as his "friend and companion." This allows Rhaenyra to remarry her uncle, Daemon Targaryen. But in the show, Laenor survives; in a twist, he fakes his own death (with the help of Rhaenyra and Daemon) in season one, episode seven.

The episode initially leads viewers to believe that Rhaenyra and Daemon have paid Qarl to kill Laenor, as it plays out in the book. Instead, Daemon kills a random servant (RIP, that guy) and burns his body while Qarl and Laenor act out a confrontation. Qarl escapes, and the burned body is brought in as "proof" that Laenor was killed in the fight. The final shot shows both Laenor and Qarl on a ship bound for Essos.

This is a much happier ending for Laenor, but it leaves one major loose thread: his dragon, Seasmoke.

Dragons aren't supposed to be able to bond to another rider while their existing rider is still alive

We don't hear anything else about what Laenor and Qarl are up to in Essos or wherever they ultimately wound up. To be fair, Rhaenyra is pretty busy in season two. We do, however, get a reference to Laenor when Rhaenyra and Mysaria observe a seemingly distraught Seasmoke in season two, episode two. Rhaenyra comments that Seasmoke recently started acting strangely, and Mysaria suggests that maybe he's lonely.

Then, in episode six, Rhaenyra takes her son Jacaerys' suggestion to try to find new dragonriders to bolster their army for the war against her half-brother Aegon and the Greens. She first chooses the Lord Commander of her Queensguard, Ser Steffon Darklyn, to mount Seasmoke, but the dragon kills him and rides off to find Addam of Hull instead.

Addam and his brother Alyn were introduced at the beginning of season two amid hints that they'd eventually become important. And the show finally explains exactly why they're important in episode six, which explicitly confirms that the two men are Corlys Velaryon's illegitimate sons, making them dragonseeds (a term to describe bastards of Valyrian descent, who are therefore potentially capable of claiming dragons) and the half-brothers of Laenor.

It's an exciting moment because it's set up to look as if Seasmoke is about to kill Addam before claiming him instead. But it's also confusing: Seasmoke technically should know Laenor is still alive, even if Laenor faked his death to everyone else.

Some fans think this means Laenor died off-screen

The bond between a dragon and their rider is established as sacred and, as far as we know, unbreakable in all of Martin's books.

There are dragon-lore consistencies across all the text. One is that no rider can have two dragons (for instance, Daenerys only ever claims Drogon in "Game of Thrones," though she technically has three dragons), and the other is that no dragon can have two simultaneous riders. This means in order for another person to ride a dragon, the first rider has to be dead. (There are exceptions in which the dragonrider can bring on a passenger, but that second person must be accompanied by the rider.)

After Sunday's episode, fans questioned the logic of Seasmoke claiming Addam as his new rider, saying this shouldn't be possible if Laenor is still alive.

At this point, there are two plausible options: Either Seasmoke's ability to choose a new rider when his existing rider is alive is a plot hole on the part of the show, or Laenor's gay retirement was cut short, and he actually is dead now.

Some viewers were already theorizing about Laenor having died off-screen earlier this season after Mysaria and Rhaenyra noticed Seasmoke's distress.

Of course, this is absolutely not confirmed, and HBO didn't respond to our request for comment.

As far as the show has established, Laenor is still alive, so this will just remain an apparent plot hole until the writers address it one way or the other or give us intel on some kind of loophole — maybe Addam being pretty closely related to Laenor factored in?

An alternative option is that dragons are simply not that bright after all, and Seasmoke was effectively tricked by Laenor's death, just like the humans. Or that he simply saw another handsome man of Velaryon blood and decided he must be Laenor (or decided he was close enough to be New Laenor).

"House of the Dragon" season two airs Sundays at 9 p.m. ET on HBO and is streaming on Max.