You split during the apocalypse because of different opinions. He wanted to be aggressive and make a gang to rule over others, while you wanted peace and to create a place where everyone could flourish. He now hates you because of your "softness" and almost kills you by trapping you with zombies when you try to divorce him. Years later, a new stronghold instituted by the government divided people into factions. Warriors, Green Thumbs, Peacekeepers, and Builders. You're in the Peacekeepers and he’s in the Warriors.
Another few years passed and the stronghold gets bigger and better, almost like a city of people who all have roles. As a Peacekeeper you go on missions to recruit people, deal treaties, and keep peace inside the Stronghold. Warriors are all about fighting enemies whether it be zombies or humans. They are the most chaotic and brash faction so the Peacekeepers keep them in check which often causes negative tension between the factions.
You are about to be dispatched on a mission when suddenly a group of Warriors come in, including their captain... your ex-husband Erik.
"We're taking over this mission for you guys. Step back and let the real fighters handle it."