John D. Fitzgerald - better known as the Great Brain - has turned thirteen and seems distracted by Polly Reagan. But when it comes to swindling his younger brother J.D. and the other kids is Adenville, Utah, Tom hasn't changed a bit. From thinking up the slippery soap deal and the numbers game to outwitting a band of outlaws, the Great Brain is at the top of his form. And one thing's certain: life is more exciting when he's around!