"The Grand Mountain Adventure Challenge" begins with Zoe and three other teams competing. From the beginning, things begin to go wrong for each of the teams. One by one, each of the other competitors gets into some kind of trouble and Zoe and Harvey have no choice but to put their own progress on hold while they save their friends. They discover that these mishaps were no accident and come to realize that one team is cheating. With the help of their friends, now out of the race, but committed to seeing Zoe and Harvey win, the kids make up the lost ground and end up in a close race with the cheating team. Letting Lassie lead the way, the kids choose a route through the wilderness that is impossible for the other team to follow. Lassie and the kids beat the cheating team and win the money to save Aunt Kim's mountain lion rescue program.