The Birdwatcher. The Smolder

Out west in Northam during the reign of Greenley the Third, Renzo's main job is to count birds for the government. He has no idea that his post was originally set up to protect the bridge down the hill from his cabin - but the Subterran civilization living more or less under his feet knows. And they're tired of living in hiding. Julia, who lives across the river from Renzo, is a government cattle herder.
She is about to make Renzo's life very complicated. Neither of them know anything about their unseen neighbors, or the civilization the Subterrans have kept alive despite decades of oppression. That's about to change. Everything's about to change. This is the 2025 revised edition. The Forgotten Ways is a sequel to this book.