When Milo the cat loses his favorite ball of yarn, Mouse offers to help him find it. But Mouse does not seem to understand that a ball is round like a circle--or maybe he is just not letting on? On the right side of the page, a pull-tab shows a fellow mouse busily pulling one end of the ball's yarn into his mouse hole, and gradually wrapping it up into a ball/circle. But in between then, Mouse proudly proclaims his discovery of a series of non-circle shaped items that he wraps with the other end of the yarn--i.e. a triangular slice of pizza, a square piece of cheese, a rectangular candy bar, an oval egg, etc. Just as Milo fears that his ball/circle is forever lost, the sneaky mouse rolls it out for him to discover.