During a game, the boys begin fighting and Flip is knocked out by a rock thrown by Rudy, who makes Timmy and Sam believe Flip is dead and it's their fault, so the two boys and Lassie run away to avoid disgracing their families.

The Martins' weekend camping trip turns dangerous when a treacherous fog envelops their camping area--and Timmy, stuck in a sinkhole in the swamp while searching for Lassie, is threatened by a maurauding wolf.

Timmy befriends the hermit who recently moved into the area, a man a visiting construction worker and his son scorn.