The main character is the Midwich Cuckoo, a Nest who has been designated as a "Quill," someone who will write about them. He is also given two targets - potential Nests - to watch.
He lives in a house with three other Nests - Kestrel, the "Covert" who is good at undercover work; Tern, the "Beak" or muscle of the flock; and Nightjar, the "Crest" or leader of the flock. Cuckoo gets his orders from the Bleak Shore itself though, so there is some friction. Nightjar does give him another target to watch, however, which Cuckoo quickly figures out is a Camper.
After watching his targets for a few weeks, the house hosts two of the more dangerous Nests, only called the Mother and Child. A week later, the house itself is attacked by a group of seemingly normal looking men with torches and flaming arrows. All the Nests escape, but Nightjar wasn't in the house at the time.