Tom, Peter, and Kit camp in the Stronghold. Peter’s family and their loyal neighbors, the Bells, secretly supply food and keep their horses. Peter, Kit, and Tom keep watch on Sir Philip’s peel tower nearby and Kit and Peter are amazed by Tom’s telescope. After two days of nothing happening, they go to explore the tower. Tom sees signs that riders have visited very recently and starts to pick the lock. Peter hears horses coming and they flee. Watching from the bushes, they see Sir Philip, Vicars, and two other riders enter the tower. Back at camp, the three friends eat and make notes, then set out to keep watch on the tower. Many other men join the first party. After night falls and the men leave, Tom determines to break into the tower. He instructs Peter to keep watch on the bridle path and hoot like an owl if anyone approaches. After waiting all night, Peter returns to camp, but Tom doesn’t.

Peter and Kit decide that Peter will go into the tower to look for Tom while Kit keeps watch.