Iceman, Beast, and Marvel Girl are training in the Danger Room when Scott) enters the room to commend them on the mastery of their abilities, when Scott notices that Warren is not present in the training session. Fearing something is wrong the X-Men search the mansion to find out where their teammate is and find Warren -- out of uniform -- glued to the television. He is watching a news report of an Antarctic expedition.
The expedition has found one of their numbers missing, however they find the mission scientist and a startling discovery: the missing man has been rescued by a strange muscle bounded human wearing only a loincloth and accompanied by a sabertooth tiger. Startled by the large and heavily armed convoy, the strange jungle man and his pet attack the other scientists before vanishing in the winter wastelands.
Theorizing that this strange man might be a fellow mutant, the X-Men tell the news to Professor X, who consents his students to go to Antarctica by themselves to investigate. While the others cheerful rush out of the Professor's study, excited to be heading out on another adventure, Scott stays behind wondering if the team is ready to go out alone. The Professor reassures and gives Cyclops his blessing that the team is ready to go out on the field without the Professors physical presence and supervision and commends Scott for his leadership skills.

Sometime later, the X-Men arrive in Antarctica and travel across the frozen wastes in a Arctic-cat until they arrive at the location of the jungle man's attack. Investigating further on foot, they uncover a crack in the ice, which Cyclops blasts open wider with his optic blast and the team journeys into what appears to be an ice cavern. Along the way they come across dinosaur bones that impossibly young, and even more surprising at the end of the tunnel they find a prehistoric jungle in the middle of the antarctic.

Flying up to scope the place out, Angel soon finds himself targeted by a swarm of pterodactyls. However a combination of Angel's fast flying and Cyclops' optic beams send the creatures fleeing. To the X-Men's surprise they find many prehistoric animals long thought extinct in this strange "Savage Land". Angel scouts ahead further while the rest of the team explores on the ground.

The X-Men are soon attacked by the Swamp Men, a tribe of hunters who have superior hunting skills that ride on giant bird beasts. They easily get the drop on the X-Men, knocking most of their numbers out with swamp gas and kidnap Marvel Girl. Witnessing the battle, the jungle man -- named Ka-Zar -- goes to the X-Men's rescue with the aid of his tiger Zabu.
When the X-Men revive, Beast thanks Ka-Zar and puts a hand on him, which offends the jungle man enough to prompt him to attack the X-Men. The heroes are then forced to subdue their savior, however their fight is quickly ended when Ka-Zar's mortal enemy the ape man Maa-Gor appears, and Ka-Zar easily defeats him in single combat and sends him fleeing. After the battle, Ka-Zar agrees to help the X-Men free Marvel Girl from the Swamp People.
While elsewhere, Angel continues his scouting of the Savage Land when he too is captured by the Swamp Men and brought back to their village. There he is reunited with Jean and the two are brought to the top of a hill where they are to be sacrificed to a deadly Tyrannosaurus Rex. The sight of the creature frightens Jean so badly that she cannot concentrate enough to use her telekinetic powers to free herself and Angel from their bindings.
The other X-Men, Ka-Zar and Zabu soon arrive outside the Swamp Men's village and mount an attack, smashing through their defenses with relative ease. As this is going on, Jean manages to compose herself to use her telekinetic powers to trip up the T-Rex and free herself and Angel.

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