Gretchen is a seven-year-old girl who loves to explore the world around her. Her best friend and cat, Lucy, joins her on her many adventures. Together they always find new things to learn about. In this story, Gretchen wonders what makes the wheels of a car turn. Her mother explains how power for the car is made. They will discover that a car works a lot like a bike. Join Gretchen and Lucy as they learn how a car works.