The Buried Giant by Kazuo Ishiguro

The Romans have long since departed, and Britain is steadily declining into ruin. The Buried Giant begins as a couple, Axl and Beatrice, set off across a troubled land of mist and rain in the hope of finding a son they have not seen for years. They expect to face many hazards - some strange and other-worldly - but they cannot yet foresee how their journey will reveal to them dark and forgotten corners of their love for one another.