Originally designed as a "digital paradise" , the location of Lyoko is under serious threat.

The computer the was used to create this world -XANA- has a bug. It has decided to claim it's independance and is out to conquer Earth! Meanwhile, inside Lyoko, the virtual human creature, Aelita, has been busy fighting the super-computer alone.

At long last, she is recieving help from OUR WORLD a bunch of earthling school kids know all about Lyoko and XANA's evil intentions. Their names Yumi, Odd, Ulrich, and Jeremie.

These four kids lead a double secret life
They are regular students during school hours, becoming world-saving hero's the rest of the time!
If they were to tell the authorities about the danger Earth was in Lyoko would be destroyed immedietly!
Which means Aelita would disappear along with it...never to return!

Now however with Aelita in the real world, their problems only increase as Yumi, Odd, Ulrich, Aelita and Jeremy continue their fight with X.A.N.A with new powers and enemies as they try to stop X.A.N.A. once and for all.