Warning: major spoilers ahead for the Season 7 premiere of Game of Thrones, called "Dragonstone."
Game of Thrones has finally returned to the airwaves after more than a year of hiatus, and the Season 7 premiere set the stage for what are almost certainly going to be some seriously bloody battles. The various factions of the Seven Kingdoms are poisoned to continue their in-fighting, even as the Great War brews to the north. We can be sure that plenty of people are going to die courtesy of epic battles and long-awaited showdowns. That said, "Dragonstone" also featured a hint of a horrifying fate for many people that none of us could have seen coming. A plague may be coming to Westeros courtesy of Ser Jorah Mormont.
Ser Jorah Momont only appeared in "Dragonstone" for a few seconds of one scene, and it would be easy to forget all about him in the grand scheme of everything else that happened. Still, that one quick scene could be the first hint that a contagion is coming that will result in the deaths of a lot of people. Jorah has been afflicted with the highly contagious disease known as greyscale for a couple of seasons now, having contracted it when he was trying to bring Tyrion to Daenerys when she was still based in Meereen. She dispatched him in Season 6 to find a cure for his disease, and we didn't see him afterward. From the look of his arm in "Dragonstone," he was quite clearly unsuccessful in finding that cure.
Unfortunately for Sam, we got the glimpse of Jorah's arm when he reached out from what seemed to be a cell in the Citadel, grabbed Sam, and demanded to know if Daenerys had landed in Westeros yet. We don't yet know how he came to be locked away in the Citadel or even what brought him to Oldtown, but it's quite possible that the maesters at least know enough of the disease to have contained him without getting infected themselves. If Jorah is to learn of Dany's landing at Dragonstone and escape, he could easily spread greyscale throughout Oldtown before he moves on his merry way.
Alternately, he could make contact with an unwary visitor at the CItadel. Gilly and baby Sam are both there, and we know from earlier seasons that wildlings and babies have been afflicted by greyscale. Gilly certainly wouldn't know how to protect herself or her child the way the maesters would. Surely somebody is going to catch and spread greyscale! It's difficult to imagine that the folks at Game of Thrones would have brought Ser Jorah back in a highly-populated area, showed his scaly arm, and had him make contact with a major character if they didn't intend to spread his disease.
Ser Jorah bringing greyscale into the Seven Kingdoms after catching it in Essos would connect to a story that has unfolded in the A Song of Ice and Fire book saga. In the books, a character by the name of Jon Connington caught greyscale after being attacked by stone men on a river, just as Ser Jorah was, and he also brought the disease to Westeros with him. The books haven't actually gotten into his story in Westeros just yet, as George R.R. Martin hasn't yet completed The Winds of Winter, but Jon Connington could well be bringing a plague with him to the novels. Ser Jorah could definitely serve the same purpose in the show.
If this theory is correct and Ser Jorah will be spreading this incurable disease to Westeros, then the citizens of the Seven Kingdoms have something new to fear beyond armies and monsters and the cold. No amount of swords or arrows or Valyrian steel blades can stop a contagion, and anybody can theoretically catch and be killed by greyscale. Even if Dany does win the Iron Throne, she might have lost a sizable chunk of her people due to Ser Jorah's attempts to aid her. We'll have to wait and see.
For more of what happened in "Dragonstone," check out our breakdown of all the biggest Game of Thrones Season 7 premiere moments. You can catch new episodes of Game of Thrones on Sundays at 9 p.m. ET on HBO, and our summer TV premiere schedule can point you to your other viewing options.