Frederick is an artistic and imaginative little mouse. While his family gathers food for the winter, Frederick sits around observing. The other mice criticize him for being lazy, but Frederick insists that what he's doing is important—he's collecting words and colors. When winter finally comes, of course, the food Frederick's family gathered sustains them. But eventually the food runs out and it is Frederick's vivid memories of the colors of spring, as well as his poems and stories, that take the other mice's minds off their troubles and get them through the winter.
In one sense, this is the complete opposite of the fable The Ant and the Grasshopper, in which we learn "he who will not work should not eat." But we think the author has a point: society needs artists as well.