 Widowed forest ranger Rick Marshall and his two children, Will and Holly, are enjoying a rafting trip when they accidentally fall over a waterfall. However, instead of being killed they somehow fall through a dimensional doorway into a closed universe populated by dinosaurs, ape men known as Pakune and a race of lizard like men known as Sleestacks. The Marshalls make the most of their time there as they try to find a way home for the next two years by using a monolithic chamber known as a pylon which acts as a doorway to other worlds. However, one day Rick tries to use one of them to try to get back home and disappears. However, Rick s brother Jack who has been searching for them lands in the Land of the Lost and joins his nephew and niece in trying to get back home.