The zombie story was very simple. After reaching the safe zone, the protagonists rested a bit before encountering a zombie tide that destroyed the boundary wall, killing many people along the way. They had no choice but to use all the manpower to protect themselves, but some of the close survivors died on the way.
Soon, they had to find some other place for survival since the current safe zone was destroyed. After traveling for another week, they finally found a safe zone with more security than the previous one. They even had cars and petrol. It was likely that some people with more electrical power were putting their energies to use.
After settling down, the safe zone leader heard what had happened to the other safe zone and lamented. He also crafted a plan saying they would go out in groups to spy on the zombies and determine how things actually worked.
Neil was chosen as one of the leaders of one such group, and he took off with the female lead.