While watching the Habitat for Humanity volunteers build a house in the empty lot next to her house, Rosa and her new friend Matthew decide to fix up Rosa's tree house.
Until he learns more of what they are doing, a young boy is upset that his special Saturdays with his parents change when they volunteer for Habitat for Humanity.
Illustrations and text provide information about seventeenth and eighteenth-century construction techniques and tools, discussing every aspect of home building, from choosing trees to finishing work.