Single-minded Jon Snow
Jon, meanwhile, has been on Dragonstone for an indeterminate amount of time. Last week's episode played it fast and loose with the timeline, so we get news about Casterly Rock this episode after getting news about Euron's attack the previous episode...yet Jon Snow is restless like he's been there a few weeks, and he's just gotten around to finding the huge cache of dragonglass in Dragonstone. Restless Jon Snow isn't new, but hanging-around-somewhere-that-isn't-The-Wall-and-knowing-what-he's-talking-about Jon Snow is like a brand new character.
This week in Jon's quest to get everyone to believe in the Boogeyman includes cave drawing-style illustrations by the Children of the Forest that reveal how they teamed up with the First Men to defeat the White Walkers. This conflict has been hinted at throughout the show, and the patterns on the wall connect these incidents with the patterns made by the White Walkers and the Children, which we came to understand through Bran Stark's flashback to when the Children of the Forest created the White Walkers to combat Men who were chopping down weirwood trees. Of course, Jon doesn't know any of this, and we don't know if it will be helpful. We don't know what location the Night's King and the first White Walkers were created in, but if Dragonstone has always had that much Dragonglass, the cave drawings Jon finds might not be the story of two races uniting to turn back The Long Night so much as a confession about the whole mess between nature, humans, and the magical weapons they wield. Maybe the dragonglass heart of Dragonstone was mined and became the hearts of those first White Walkers.
Another thing Bran knows that Jon doesn't is that he's flirting real hard with his Aunt this episode. It's official, "Bend the knee," is becoming Westerosi double entendre between these two. It's less in the words than it is in the performances, but when Dany asks Jon for advice this episode, it's clear she's begun to respect him, and that he can even vault Tyrion in her esteem if the time is right. That's a lot of trust in a rebelling King of the North for Daenerys to have, but it's probably easy because Jon's only interested in one thing still, which he maintains to Davos in this episode. Jon may be feeling out Dany's morals and tactics, but only to get troops for the war with the Army of the Dead.