A dinosaur likes a certain kind of fruit, so the cavemen tell the Butlers not to take any of that fruit. Greg decides to take a bucket of it into a cave and the dinosaur causes a cave-in trying to get it.
The cave has no other exit and is filling with water, so Mrs. Butler decides to make a syphon out of a bunch of bamboo jammed together. Luckily they are able to get it air tight and put it through a hole in the roof and it is able to drain the cave super quickly just as a way out is found.
Greg teaches the natives the proper way to dig for taro roots.
Army ants threaten the whole valley, so the Butlers decide to build a hot air balloon out of snake skins from a cave and a lot of thread that they just have and it's not buoyant enough to carry everyone's weight but they still decide it needs a huge basket made out of wood.
Just as the ants are about to eat them they finish the balloon and fill it with heat from a forest fire they have set.
They need to make two trips to get everyone to the top of the hill.
The first group to go up detaches the grappling hook from the balloon and keeps it on the top of the mountain, so it is really hard for the second group to land in the wind because they have also detached the guide rope that they used to pull the ballon back down the mountain.