When news reports start appearing of a zombie outbreak in Ireland, B's racist father thinks it's a joke-- but even if it isn't, he figures, it's ok to lose a few Irish.
B doesn't fully buy into Dad's racism, but figures it's easier to go along with it than to risk the fights and abuse that will surely follow sticking up for Muslims, blacks, or immigrants. And when dodging his fists doesn't work, B doesn't hesitate to take the piss out of kids at school with a few slaps or cruel remarks.
That is, until zombies attack the school. B is forced on a mad dash through the serpentine corridors of high school, making allegiances with anyone with enough gall to fight off their pursuers.