Fern and Horn are twins who look like two peas in a pod or two stars in the sky. But Fern and Horn have different ways of seeing the world. They try to outdo each other with imagination and improvisation, using crayons and pencils, ripped-up paper and cardboard boxes. Fern loves to draw flowers and butterflies, birds and bees, caterpillars and orange trees. She draws here, there and everywhere. Horn wants to draw too, but he thinks his flowers look like purple pancakes and his caterpillars like striped socks. "Draw whatever you want!" Fern tells him. Horn draws an enormous elephant that tramples all over her pictures. Fortunately, Fern's imagination is as big as the universe. She loves gazing at the stars and making star shapes. Again, Horn tries to follow suit, but he is frustrated with his creations and makes a ferocious paper polar bear that devours Fern's stars. Undeterred, Fern decides to build a castle that can withstand elephants and polar bears, but a fire-breathing dragon comes along. Luckily, Fern knows exactly what dragons like best.