Blind Sided: Book 4 of the Irish End Games;

When the world comes crashing down around you, it’s important to believe in something…
After four years of living in a post-apocalyptic world, one thing Mike and Sarah know is that nothing ever stays the same. Just when life had begun to settle down—and all their immediate needs met—a threat comes at them from a totally unexpected source. Not England or roaming bands of thugs, not the US or even the Middle East. This time it’s the land itself—the very bushes and trees of Ireland--that they’ll have to protect themselves from.