The Alden children, Henry, Jessie, Violet, and Benny, decide to enter their dog, Watch, in a competition to star in dog food commercials.  Watch’s main opponents are Ninja, the star in a TV show, and Buffalo, owned by a boy.  As the story unfolds, there are a couple of mysteries about the contest for the children to solve.  This is book 121 of t he Boxcar Children series created by Gertrude Chandler Warner.