Students Yumi, Jeremy, Odd and Ulrich stumble across a large Supercomputer in an old factory by their school. They soon discover that the computer houses an alternate world, Lyoko, and that by using computer controls they can transport themselves into this virtual universe. Once inside, they meet a virtual humanoid girl named Aelita who relays the story of X.A.N.A., a sentient virus that has infected the Supercomputer and threatens to destroy Lyoko and ultimately control the Earth. They spend four seasons battling the elusive X.A.N.A., developing new methods and technologies for entering in and out this alternate universe and protecting their classmates, teachers and the world as they know it. Audiences, meanwhile, hang on with anticipation as the question looms- can our heroes put an end to the treat of X.A.N.A.? One thing is certain: they are ready to risk everything to win.