In a small Cornish seaside town in early December, wounded war veteran Nat Hocken is working part-time for a farm owner when he notices a large number of birds behaving strangely along the peninsula where his family lives. He attributes this to a recent cold snap and the sudden arrival of winter. That night, Nat hears a tapping on his bedroom window and encounters a bird that pecks his hand, causing him to bleed. As the night progresses he encounters more birds, especially those flocking into his children's room, but the birds leave at dawn. Nat reassures his wife that they were restless because of a sudden change in the weather.