Xan and Oz are two friends that live inside a fortified city, protected from the outside world.

One day, some intruders cross the wall, which allows Xan to escape, forcing him to leave Oz behind.

Oz will try his best to see his best friend again, but in order to achieve that, he'll have to resist the tyrannical intruders of the outside world, who will try to dominate the city and turn it into a lifeless version of what Oz and Xan considered to be a home.