Two young naturalists on a quest for something extraordinary. There’s room for just one final piece in Winslow and Rosie’s impressive collection of natural wonders. So, they set off into the forest in search of something extraordinary. They journey far — along the creek, across the valley, through the spruce grove and up the mountain. And while they find many extraordinary things, nothing is just the right extraordinary thing. When the girls find a deep, dark cave, they decide to venture farther than ever before. Surely, a mysterious cave must hold something extraordinary … It takes clever collectors to recognize a treasure — especially in the most unexpected place!