Ten-year-old Ieuan and his friend Maldywn are peacefully growing up in the Welsh Marches, climbing the waterfall near their home to glimpse the hills, pastures and, of course, the many flocks of sheep below. Then one day, on the moor, they meet a sheep unlike any other. Ovis takes them on fantastic journeys and introduces them to people so unbelievable and so faraway from their little village that they can scarcely distinguish between fantasy and reality any longer. So, when reality eventually closes in and the boys grow up, leaving the mystery and magic behind them, they find that their adventures continue to haunt them. Has that first innocent trip beyond the waterfall changed the course of their lives for ever?