Mr. Z is trying to take all of the zeros away with him. Jackie, Matt, Inez, and Digit discover that zero has meaning just like any other number. They use real-world examples, such as telling time or taking an elevator to the 10th floor, to show what will not be possible without zero. On their search for Mr. Z, they note that the cars on a highway are traveling very slowly because the zero from the original speed limit, 60, disappeared.