The zombie plague started when Abraham Reyes stole the mask from the Catacombs. In the mission "A Civilized Man" John goes to Escalera and finds Undead Abraham chasing a women and John kills Undead Abraham. A women explained that he stole a mask that makes him invisible. John and the women goes to the catacombs to put the mask back where it was. However, John must kill a group of Undead and Mummies when on there way to the end. When they reached to the end, John kills the last of the Undead and Mummies and they both put it back where it was. And John finds out that a women disappeared and the women reveals her name is Ayaunteol and she told John to go back home. When John comes back to his hometown he finds that Jack and Abigail are back to normal and the zombie plague ended. A few months later Seth steals the mask and John died and he came back to life as a zombie causing the zombie plague starting again.