Jon and his ill-fated search party make their way beyond the wall toward the great unknown. Tormund Giantsbane muses about how to survive in the wild tundra, his former domain, and tells Jon not to make the mistakes the former King Beyond The Wall Mance Rayder made because of his pride. Jon also talks to Jorah and offers him Longclaw, the ancestral Valyrian steel sword of house Mormont, given to him by the late Night's Watch commander and Jorah's father, Jeor Mormont. Jorah refuses. "I brought shame onto my house and broke my father's heart," he says. "I forfeited the right to claim this sword." Jon stops to brood and the party presses onward.
The party continues to chat, providing some of this season's best dialogue thus far. Tormund learns a new word (not safe for a family newspaper) and lays out his plans for wooing Brienne of Tarth. Beric and Jon swap resurrection tales and Beric does his best to assuage a perplexed Jon, who doesn't know what it is the Lord of Light brought him back to life to do. "Death is the enemy," Beric says. "The first enemy and the last … The enemy always wins and we still need to fight him — that's all I know."
In the distance, a mountain emerges — the one The Hound saw in the flames earlier this season. A far-off blob appears in the swirling snow and begins a fast advance toward the group. From the swirling storm, an undead bear roars forward and the group begins to fight it. The party loses several unnamed members and Thoros takes a deep bite to the chest. Beric cauterizes his wound and they journey toward the mountain.
In Winterfell, Arya and Sansa continue to show there is no love lost between them. Arya reads Sansa the raven scroll Sansa sent to Robb years ago when she was a Lannister prisoner. Arya, with all her wit and supposed ability to discern the truth, cannot accept Sansa's explanation — that she was young and under duress. Arya sees only Sansa's supposed ambition to unseat Jon and makes a subtle threat to tell the Northern lords about Sansa's treasonous message.
Sansa goes to Littlefinger in dismay. He suggests perhaps Brienne could be of help to the sisters, since she is pledged to protect both of them. Sansa agrees that she would intercede, but later sends her as a representative to a meeting in King's Landing.
On Dragonstone, Tyrion tries to convince Daenerys to temper her anger and impulsiveness just a tad, which she receives about as well as you'd expect. Tyrion wants Dany to pick a successor, as she is (supposedly) barren and needs a way to carry out her goals should she perish in wars to come. Having none of this, she tells Tyrion they can talk succession when she's crowned Queen of the Seven Kingdoms.
While Dany and Tyrion chat about heroism, the heroes beyond the wall have backed themselves into a losing situation. The party encounters a group of wights and a white walker. They kill the white walker, which shatters all of the undead soldiers except for one. That wight becomes a prisoner, the proof they'll bring back to King's Landing to convince Cersei to ally herself with them against the Night King. Only problem is, this little guy puts out a mountain-shaking distress call and the rest of his undead buddies come to back him up. As the Night King's army approaches, Jon sends Gendry back to Eastwatch, where he sends a raven to Dany. "Daenerys is our only hope," says Jon. Beric mentions they might be able to take out the whole army at once if they kill the Night King, as killing a wight's creator seems to end the magic that reanimates the dead.
Jon and company spend the night huddled on a rocky island while the wights surround the scouting party. Thoros freezes to death, and they burn his body. The undead army are kept at bay only by cracking ice — that is, until The Hound throws a rock and it skitters to the edge of the cracked ice, where the ice holds up. The dead rush forth, and the party does its best to beat back the onslaught. Just when it looks like everyone's pretty much doomed, Dany swoops and takes out the wights with dragonfire.
The Night King, apparently an expert javelin thrower, launches an icy spear into Viserion and the dragon crashes into the icy water. As he queues another spear for launch, Dany flies away with Tormund, Jorah, The Hound and Beric. If you're wondering where Jon is, some wights have just pulled him into the water. It's a good few heart-attack-inducing seconds before he emerges, but he does and with steely resolve. Jon charges (limps, but the intention is there) toward the Night King, who I'm sure is bemused by this frail human's attempt. The wights turn back toward Jon and swarm again. As they fall upon him, out of nowhere Benjen gallops back into the storyline for a brief, shining few seconds. He gets Jon aboard his horse and sends him back toward Eastwatch. Benjen fights the wights best he can, but they soon overtake him.
Back at Winterfell, Sansa discovers Arya's faces and Arya discovers Sansa snooping. Arya reveals to Sansa where she's been all this time and what she learned while training with the Faceless Men in Braavos. Arya makes it perfectly clear that she could kill Sansa whenever she wants and advances toward her with Littlefinger's dagger. At the last minute, she pivots the hilt toward Sansa and offers it to her. Sansa takes the dagger, and Arya strides out the door.
At Eastwatch, with Dany sitting beside Jon's recovery bed, she sees the scars left by his assassination attempt. Jon opens his eyes to see Dany sitting there. He apologizes to her, telling her he wishes he could take it all back. She waves him off, saying, "If we hadn't gone, I wouldn't have seen. You have to see it to know. Now I know."
Dany pledges her support to the fight against the white walkers and Jon, in turn, bends the metaphorical knee. They share a lot of demure looks and lingering hand squeezes before Dany rises and strides out of the room to let Jon rest.
And beyond the wall, thousands of wights strain and pull at several gigantic chains (I guess they have magic metalsmiths up there). Viserion emerges from the depths and the Night King walks to the dead dragon. He places his hand on Viserion's head. A few moments pass and suddenly, Viserion's eyes snap open, now a glowing, icy blue.