Tic-Tac-Tom wins every game of tic-tac-toe he plays. He even has a shirt that says "Tic-Tac-Tom The World's Greatest Tic-Tac-Toe Player"! Brother, Sister, Cousin Fred, and Lizzy Bruin wonder if Tom might be up to some sneaky tricks. With careful investigation and a little help from Dr. Wise Old Owl, they just might get to the bottom of the tic-tac-toe mystery.