When the old Tooth Mouse announces that it is time to name her successor, Sophie, the small mouse who would NOT go to bed, desperately hopes to be chosen. The three tasks she is assigned are difficult and dangerous, and some of the other mice believe that she is just too little to succeed. At times, Sophie even doubts herself. But sometimes, the wisest answer really is the simplest one -- and sometimes the best mouse for the job just might be the very smallest one.