Outfitted only for a short camping trip, the resourceful family from California takes shelter in a natural cave and improvises the provisions and tools that they need to survive. Their most common and dangerous encounters are with dinosaurs, particularly a "Tyrannosaurus rex" they nickname "Grumpy", which frequents the location of their cave. However, many of the dinosaurs are herbivores, posing no threat to the Marshalls, unless unintentionally provoked. One is a particularly tame young "Brontosaurus" that Holly nicknames "Dopey", and upon which Holly looks as a pet.