The episode opens up with a montage of Merlin himself making the Amulet of Daylight, along with an unseen assistant. Forging it, engraving it, and assembling it. And for the finishing touch, he recites an incantation that empowers it with the magic of daylight.
In present day Arcadia Oaks, everyone tries to understand why its destruction is the only way to find Merlin's Tomb. Jim decides that maybe he doesn't need to destroy it since Gunmar is holding AAARRRGGHH!!! captive. Claire could use him as an emotional anchor to portal jump straight to him. Hence forth, their plan is set: Rescue AAARRRGGHH!!!, find Merlin's Tomb, and get the Staff of Avalon before Gunmar does.
Jim, Claire, and Toby say goodbye to their parents before they depart on their trip with Blinky. Upon reaching their destination, they find AAARRRGGHH!!! in a stasis trap surrounded by a dozen Dwärkstones ready to blow. He tries to tell them to leave, but they refuse to leave their friend behind. Jim notices rats heading down a crevasse in the cobblestone flooring, concluding that they have to be going somewhere.
As Jim comes up with an idea, Angor Rot is leading Gunmar and Draal through the path to the mountain's chambers. Upon arriving at a cave behind the waterfall, Gunmar reads an engraving above the entrance: "In this place of my final rest, no magics here may enter". Just then, Draal awakens from his trance, as if the Decimaar Blade's hold on him has been severed. Upon noticing Draal recovering, Gunmar tries to summon it, but to no avail, and the two trolls duke it out while Angor Rot smugly watches. Just as Gunmar is about to deliver a killing blow, something he says ("You are a dog, and this is your leash!") makes Angor Rot stop him, claiming that Draal could still be useful.
Back in the chamber with the Trollhunters, Jim lays out his plan for freeing AAARRRGGHH!!!. It works narrowly, with the stasis trap breaking, and the floor collapsing just in time before the stones explode. After feeling a sign of relief to have their friend back, the gang discovers they've landed in an ancient gyre station. Blinky notices that the gyre doesn't have any controls, until he realizes there's a spot reserved for the Amulet of Daylight, or at least the blue gemstone inside the amulet's metal frame. Blinky reminds Jim the consequences of destroying the sacred Amulet of Daylight if this doesn't work, but he prioritizes the Staff of Avalon above all else, and smashes the amulet with Toby's hammer. Jim places the blue gem in the spot, revealing a map and powering the gyre.
Back at Jim's house, Strickler is telling everyone the story of when he fought Jim for real while on a dinner date with Barbara. Suddenly, she gets a text from Jim saying that they're fine.
Back in the caverns, the gang arrives at the entrance to Merlin's Tomb. However, all their weapons begin failing as the cave repels all magics. Things get better when they realize that this also means Draal is free from Gunmar's control, and they set out to rescue him once and for all. The tunnel takes them to an old room. The only way forward is through a top window with no way of reaching. While exploring, Toby steps on a tile that changes the room completely. Upon holding it down, it makes the entire room jump into the past, and Blinky deduces hundreds of years. When Toby weighs down the tile with a bag of seeds, Claire figures out how to surpass this challenge. She plants the seeds in a pot, has everyone step back, and Toby takes the bag off the tile. When the room returns to present day, the seeds have grown into enormous vines that gang are able to use to climb up and out through the window.
The next room has engravings all over the walls, depicting all the events that lead to the exact moment. In fact, the timeline even goes beyond the present. Unfortunately, things get ugly when they find pictures of them with Angor Rot hovering above them, meaning that this exact moment is when the Trollhunters engage in another fight with him in that exact chamber. However, with no functioning weapons, they have no way of fighting him. But AAARRRGGHH!!! gives him the slip when he punches a wall and buries him under rubble. Toby finds Draal's mechanical arm lodged within a doorway in the floor. Jim removes the prosthetic and opens the doorway, only to find that it's blocked by spinning blades. As Angor Rot digs himself free, Jim puts Draal's arm back into the blades to jam them long enough to slip past them unscathed and finally land inside the central chamber: a huge gaping crystal engulfed abyss.
As the gang take a moment to appreciate the beauty of the innermost sanctum of Merlin's Tomb, Jim deduces that the Staff of Avalon and Draal can't be far. He goes on to look for him while Blinky leads everyone else to search for the staff in the only direction they can: down. The search is progressing rather slow. However, Jim successfully locates Draal, unconscious and wedged in a pile of crystals. While Angor Rot finds a way inside the sanctum, Draal awakens and blames himself for what happened after being touched by the Decimaar Blade. He swore an oath to protect Jim, but believes he has broken it and failed everyone. As Jim reattaches his arm, he soothes his sole by reminding him that none of it was his fault, as Gunmar had him under his control. Jim tells Draal that he is more than his loyal protector, he's a trusted friend, and the boy and the troll share a hug.
As the warriors hear Gunmar's voice, Draal vows to make him taste vengeance, and they cheerfully resume their search for the staff. While climbing down the abyss further, Jim has the staff in his sights, but also Gunmar ready to take it. Draal handles him while Jim goes for it first. Jim successfully claims the Staff of Avalon, but their victory is cut short by not only the sanctum beginning to collapse, but also the arrival of Angor Rot. A fight ensues with Jim holding his ground against him, and with Draal handling Gunmar just fine. However, Jim loses his advantage, but Draal comes to the rescue and saves him from the bloodthirsty troll assassin just in time. With both enemies momentarily incapacitated, Jim playfully challenges Draal to a race back to the top, to which he happily accepts. A few close calls with Angor Rot don't slow Jim down, but as Draal is about to help him up, he is blindsided by Gunmar. He's badly hurt, and the gang arrives too late as they watch Gunmar pluck the staff from Jim's hands.
While he gets away with it, Angor Rot appears and prepares to strike Jim down. Seeing this, Draal races to the rescue but ends up being struck straight in the heart by the assassin's deadly creeper sun dagger meant for Jim. With Angor Rot in his grip, he asks Draal why he would give his life for a human. Turning to stone, he replies "Because, he's... my FRIEND!!!". Claiming it has been an honor, Draal bids Jim a tearful farewell and falls backward with Angor Rot still in his grasp. He breaks free, and Draal completely solidifies, leaving his lifeless stone body to fall into the empty foggy abyss below. Gunmar leaves Angor Rot behind, claiming he has served his purpose, and takes off with the Staff of Avalon. With Jim heartbroken over his surrogate brother's ultimate sacrifice, Blinky tells him that they must now find a way out, as the staff was the only thing holding the sanctum together. With the whole cave falling apart, the gang makes their hasty escape, but are halted by debris.
- Kelsey Grammer as Blinky
- Emile Hirsch as Jim Lake Jr.
- Charlie Saxton as Toby Domzalski
- Lexi Medrano as Claire Nuñez
- Jonathan Hyde as Mr. Strickler
- Fred Tatasciore as AAARRRGGHH!!!
- Ike Amadi as Angor Rot
- David Bradley as Merlin
- Clancy Brown as Gunmar
- Mark Hamill as Dictatious
- Tom Kenny as Javier Nuñez
- Amy Landecker as Barbara Lake
- Andrea Navedo as Ophelia Nuñez
- Laraine Newman as Nana
- Matthew Waterson as Draal
- Anton Yelchin is once again featured in the credits, having provided Jim's interjections during the climax of the episode.
- Draal is officially freed from Gunmar's influence in this episode, but is ultimately killed by Angor Rot while he tried to protect Jim.
- According to Aaron Waltke on his Twitter page, the time puzzle room in Merlin's Tomb was originally going to be set in this scenario: Toby creates a backwards chain reaction with a cup of water, which becomes part of a flood that would "unbreak" a series of pillars leading out. This idea was scrapped because it was deemed "too insane".
- During the opening sequence of the amulet's construction, a left hand from the forearm up is in a smelting pot: the hand one would assume would be Morgana's. Plus, there is an unknown assistant helping Merlin assemble the Amulet of Daylight.
- The former would end up being confirmed by Morgana herself in "The Eternal Knight: Part 2".
- Gunmar makes the classic villain's empty threat of someone not making it out of this place alive. For once, this was no empty threat.
- This is the first episode Angor Rot actually displays empathy.