There is a virtual world parallel with ours: Lyoko

Conceived as a numerical heaven, Lyoko is seriously threatened. The computer called X.A.N.A, who leaded this world, has a bug.

X.A.N.A took its independence. This super computer now projects to take the control of the Earth. Its strategy: destruction.

On Lyoko, Aelita, virtual human creature, keep fighting the super computer: she is alone.

Soon, she received help from another world. OUR WORLD.

On Earth, a band of four schoolboys knows about the existence of Lyoko and the harmful intentions of X.A.N.A. They are YUMI, ULRICH, ODD and JEREMIE.

They carry out a double life in the greatest secret: they are schoolboys like the others per hour of studying… and savers of world the remainder of time. If the inform the authorities of the danger which threatens the Earth, there is no doubt, Lyoko would be immediately destroyed and Aelita would disappear. But for our heroes this is not an option: between them and Aelita it's a great friendship story.

To fight X.A.N.A, only one issue: to go to fight it on its area. They must go to Lyoko. YUMI, ULRICH, ODD and JEREMIE found the way to transport to Lyoko and they hope well to save both Earth and Lyoko.

Save the world - But which one?