The boisterous, arrogant professor Challenger, a reputed biologist and anthropologist, dares the London Zoological Society to mount an expedition to verify his spectacular claim, without physical proof, that his previous expedition to the Amazonian basin found live dinosaurs. Apart from him and his 'socialite' counterpart, professor Summerlee, it consists of experienced discoverer Lord Roxbury, the young reporter Ed Malone -who got publicly struck down with Challenger's umbrella at his arrival- and Jennifer Holmes, Malone's news agency's boss's daughter, essentially as conditions for putting up the money. In Brazil they are joined by Jennifer's brother David and local 'guide' Manuel Gomez. They soon discover the dinosaurs are real and dangerous, like giant spiders, but loose their helicopter and thus are desperate for a way down from the isolated plateau. They learn Roxbury knew about the fate of Burton White, an explorer whose diary they find, thus presume to be dead, in search of diamonds, and confirmation of the local tribe being the lethal guardians of the plateau's secrets, but also get surprising help...

美国政府制定一项计划，拟花费七十亿美元，建造一台可以提供时空旅行的机器。一位参议员被国会派去检查该项目进展情况，以决定政府是否继续资助这计划。由于项目的进展令议员很失望，因而项目负责人之一托尼决定