In typical Asgardian fashion, the gods hold a festival to celebrate the defeat of Loki (in Thor #194). Thor and Sif speak romantically, while the Warriors Three enjoy so much wine that Fandral decides to demonstrate his dancing prowess to all present. Amidst all the reveling, however, Thor realizes that Odin has been troubled since Loki’s defeat, and goes to visit him. With a heavy heart, Odin reveals that he must send Thor on a crucial mission that might keep him away from Asgard for all time: Thor and the Warriors Three must journey to the World’s End to learn the secret of the Twilight Well from Kartag the Keeper. Sif calls Odin cruel for sending Thor on such a mission, but Odin insists that he cannot reveal his reason. Thor accepts, and Odin uses his scepter to transport Thor and the Warriors Three away. Once he’s gone, Odin reassures Sif that he actually sent Thor on this mission to save him, not to harm him. Odin then calls upon Hildegarde to take Sif to Blackworld. When Sif protests, Hildegarde knocks her out! When Sif finally awakens, she has already been transported to Blackworld by Odin. There, Hildegarde tells Sif that she is not alone in her grief for being away from her love; Hildegarde herself loves one of the Warriors Three, although she does not say which one.
Meanwhile, Thor and the Warriors Three find themselves on a strange, foreboding planet. Thor admits that even he does not know Odin’s true purpose, but it is not their place to judge. As they journey, Thor and his companions run afoul of a gigantic, spider-like creature who calls himself Kartag’s Guard. The imposing creature knocks Hogun and Fandral from his web and grabs Thor, but Thor strikes him with a blast from Mjolnir, knocking him into the chasm below. Then, Thor flies down and rescues Fandral and Hogun before they hit the bottom. Volstagg, of course, has been valiantly guarding the rear throughout the skirmish.
Back in Asgard, Odin meets with a group of four elder Asgardian warriors—Whitemane, Khan, Bulwar, and Rongor—who have, at Odin’s request, stayed out of the limelight for years so that the younger gods could earn their own glory. With the coming danger, though, Odin has called them out of retirement. All four warriors are eager to face battle again, even if it is to be their last. That makes Odin feel better, he says, because this is all his fault: he banished Loki to the same planet where he had imprisoned Mangog. Odin shows the warriors an image of Loki freeing Mangog and offering to help him get revenge on Asgard. The powerful Mangog, however, says it is presumptuous of Loki to think he can help, then magically encases him in a block of amber! Upon seeing this, the warriors vow to fight to the death for Asgard.
To complete their mission more quickly, Thor and the Warriors Three capture some Yrrlbeasts (which look like a cross between a dinosaur and a ostrich) to ride like horses. As they ride through a forest of gigantic trees, they are attacked by trolls—not Asgardian trolls, but the scrappy, suction-cup-fingered, tree-dwelling trolls of this realm. Although the Warriors Three are holding their own against the overwhelming numbers, Thor does not have the patience for a battle, and defeats all the trolls at once with a massive blast from Mjolnir. However, after the battle, Thor hears one of the trolls crying for help as it sinks in quicksand. Thor rescues the troll because, although they had just been enemies, he cannot allow the death of a defenseless foe. The rescued troll, Kygar, vows to serve Thor. Thor only asks that Kygar take them to the Twilight Well.
Meanwhile, Hildegarde and Sif walk through the empty streets of a town on Blackworld. When Hildegarde pounds on the door of a closed up inn, the innkeeper cracks the door and tells them to hide because “he” is coming. At that moment in Asgard, Odin reflects that it feels like the calm before the storm. Just then, the Grand Vizier runs up to Odin to announce that “he” has arrived in Asgard. The issue ends with a splash page of Mangog bursting into Asgard and overwhelming its warriors.