The X-Men train their powers. Angel is watching TV and sees a man and a saber-tooth attack a reach team in Antarctica. Professor X sends the X-Men on a mission to investigate what is going on in Antarctica. When they reach the Antarctica, they find a hidden land filled with dinosaurs. A group of natives attack the X-Men and capture Marvel Girl. The wild man and the saber-tooth scare off the natives. He tells the X Men his name is Ka-Zar and his tiger Zabu. A man from the Man-Ape tribe attacks Ka-Zar but is defeated. Ka-Zar tells the X-Men that the Swamp-Men captured Marvel Girl and that they are his enemies so he will help the X-Men. Angel flies off from the X-Men to get a view of the land but is also captured by the Swamp-Men. The Swamp-Men are going to use the two X-Men as sacrifices. With the help of Ka-Zar and Zabu, the X-Men defeat the Swamp-Men and rescue Angel and Marvel Girl.

The first appearence of Ka-Zar and Zabu, and also of the Savage Land in Antarctica.