Eleven-year-old Stevie, who comes from a long line of Steves, doesn't feel as if he fits in the Minecraft world. His father is great at building and fighting off zombies, but Stevie struggles in these areas. One day, when Stevie is alone in the field trying to build something new that will impress his dad, he discovers a portal into a new world. Stevie steps out of a computer screen and into the room of eleven-year-old Maison, a sixth-grade girl who loves to build and create, but who is bullied and made an outcast by her classmates for not indulging in activities deemed cool.
Stevie is shocked by how different this world is, and Maison takes him under her wing and teaches him all about her world. The two become friends, and Maison brings Stevie to school with her. Stevie is horrified to see there are zombies in the school! He realizes that when he opened the portal, this allowed zombies to also enter the new world. More and more creatures are slipping out by the second, wreaking havoc on a world that has no idea how to handle zombies, creepers, giant spiders, and the like. Stevie and Maison must put their heads together and use their combined talents in order to push the zombies back into Minecraft, where they belong.
As Stevie and Maison's worlds become more combined, their adventure becomes even more frightening than they could have imagined.