It's time for Field Day at Bayport Elementary and all the kids are excited! Whatever grade wins gets a pizza party, and the person with the highest personal score also gets a special prize. But when the field equipment is sabotaged the day before the events are supposed to start, it looks like Field Day might not happen after all--unless someone can find out who is behind the mess of ruined rackets, tangled jump ropes, and flattened balloons. Can Frank and Joe crack the case and save Field Day?