Caillou is absorbed in his construction project. He is building a magnificent castle that he wants to surround with a fortress. But as the day goes on, Caillou has more and more trouble with his project. A nap restores Caillou's energy so that he can finish his work. A nap is a healthy and necessary component in a child's development. Children often resist napping, but a rest helps them enjoy their entire day. In this collection, Caillou grows as his universe expands. Step by step, he acquires greater autonomy.