"I've seen Greyscale before… but nothing like that."

Tyrion Lannister says what's on all of our minds following the climax of last night's "Game of Thrones." The episode, called "Kill the Boy," finally brings the simmering story of Greyscale to a boil, after applying consistent heat over the past few weeks — and it's grim news not just for one of your favorite characters, but potentially all of them.

SPOILERS from last night's episode officially ahead.

In the episode, Tyrion and Jorah travel through Old Valyria, the former seat of one of the greatest civilizations in the known world of ice and fire. An ancient doom consumed Valyria long ago, ending an advanced and vast empire in an instant. These days, it stands as the ruined home of virtually nothing, save for the Stone Men, people suffering from advanced cases of Greyscale who have been cast off into exile.

Greyscale, in case you don't quite recall the details, is the same affliction Stannis Baratheon's daughter Shireen suffers from, the reason her face features stone-like scars. It hardens flesh, eventually causes death, and incites madness all the way through to the dying day. The highly contagious disease is, apparently, treatable, as seen by Shireen's survival — but treatment is no walk in the park, as Stannis informed his daughter (and viewers) during "Sons of the Harpy" about the great many maesters and healers he relied on to save Shireen's life.

Until this week, Shireen stood out as the only main character suffering from Greyscale. Now? Not so much. While passing through Valyria, Jorah and Tyrion are assaulted by Stone Men. "Don't let them touch you," Jorah shouts at Tyrion as he battles the attackers, but the words fall on deaf ears, as one of the Stone Men drags Tyrion down into the water below.

As it turns out, it's Jorah, not Tyrion, we should worry about. The Imp survives his encounter seemingly unscathed, perhaps because the Stone Man only grabbed him by his pants leg. Jorah, meanwhile, must have made direct contact with one of his assailants, as the episode ends with Ser Mormont examining a spot of Greyscale on his wrist. Not good!

But how bad is it? Is Jorah doomed, like Old Valyria? Possibly. Stannis makes it plainly clear that saving Shireen was no small task. Right now, Jorah is far away from medical treatment. Even if he makes it to Meereen in one piece, the Slaver's Bay city isn't exactly equipped for an urgent care medical crisis. There's a lot of time for the contagion to spread, and not a lot of time or resources to contain and crush it.

So, assume Jorah makes it to Meereen. Assume he touches people along the way. Assume he makes it to Daenerys and attempts to stand in the way of her wedding day. Assume he gets back in her good graces and finally marches with her on Westeros. Assume all these things — and then consider Jorah's affliction. That's a lot of people who could come down with the sickness, isn't it?

And there's reason to believe that Jorah will make it to Westeros, or at least his disease will. In "A Dance with Dragons," the fifth book in George R.R. Martin's series, a different character comes down with Greyscale: Jon Connington, a House Targaryen loyalist who arrives in the Seven Kingdoms after several years in exile. It's Jon, not Jorah, who has a fresh case of Greyscale in the book, and his arrival in Westeros calls into question the potential spread of the disease throughout the realm.

Can we expect to see a Greyscale outbreak in Westeros at some point in the future? There's some precedent from the books for it, and there's a reason why the disease has become such a big deal on the show in recent episodes... and maybe the reason is because Jorah Mormont is about to spread his several germs across the Seven Kingdoms.

Ewww. Mormont mucus.