Martin and his family spend every Sunday together and every Sunday they have the same routine. Not this Sunday, he decides while everyone else watches TV, cooks, and folds laundry. Instead, Martin invents a world adventure with his dog, Maize, braving extreme cold alongside penguins on ice caps, facing a dragon, confronting pirate ships, and crossing an arid desert on a camel's back. When he returns from his travels happy and exhausted, he recounts his magical journey with Grandma, who marvels at his courage and wonders where he will go next.