When best friends Adam and Marky decide to explore a spooky abandoned building on their way home from school one day, they soon discover it's more than just a crumbling old factory. Inside, a terrifying monster, Herobrine, is building an army of darkness by creating hordes of zombies, and he plans to unleash his forces against the world. They're alone and scared, but they know they are the only ones who can stop Herobrine's evil desire for conquest...