Based on the novel "The lost world" of Sir Arthur Conan Doyle, this book continues Gentleman Joe's series of adventures, this time in South America. Professor Challenger, a british scientist and explorer claims that he discovered a place wgere dinosaurs are still living. Because nobody nelieves him, he propose to sent there an expedition to certify his discover. There are three volunteers: professor Summerlee, a
well known biologist, Ned Malone, a journalist and Lord John Roxton. But in the last moment, due to an accident of Roxton, he is replaced by Gentleman Joe, an american fine sniper. The squad arrives to South America, but to their surprise, the envelope with the map that Challenger gave to them have inside only a blank sheet of paper...