just asks him to listen to what he has to say and gives him his gun as a pledge of good faith. The next day, Blake takes the plane and goes to Antarctica with Professor Labrousse to take a delivery of a mysterious cargo. Meanwhile, the mysterious man is handed a passport, a plane ticket to Nairobi and cash by David Honeychurch, who has received these instructions from his superior Blake. Arriving at his destination, he settles in the same hotel as Mortimer and his two friends, and turns out to be Colonel Olrik in disguise. Meanwhile, Mortimer, Sarah and Nastasia are in the hospital to visit the delirious Dr. Heidegang. Mortimer manages to make contact with Heidegang by speaking German and learns that the guardians of Gondwana demand that the ring be returned to them. The three friends fly to Arusha, accompanied by Olrik in disguise who has managed to be invited by Nastasia. They find their guide Bombo, with whom they leave the next day in an all-terrain car for the crater of the Ngorongoro. Meanwhile, Olrik helps Uru, a young Maasai at the market, which causes him to fall into a trap. He is recognized by Razul the Bezendjas, his former henchman, who convinces him to team up to share the riches of the lost civilization of Gondwana. With the airship of Youssef, another former accomplice of Olrik, the three criminals can follow without being seen from the car carrying Motimer, Sarah, Nastasia, Bombo and Uru. When crossing a river, Nastasia falls into the water and is carried by the current to a bank downstream where she finds herself facing a lion. Uru, who has followed, fights the lion and eventually kills it before succumbing to his wounds. The young woman now faces a pack of African wild dogs and is saved by shots fired from an airship where she recognizes Olrik without believing it. Mortimer, Sarah and Bombo finally arrive at Nastasia after escaping the charge of a herd of elephants and the overthrow of their car. That evening, they attend the funeral of Uru in his village. The next day, Mortimer, Sarah, Nastasia and Bombo arrive at the Ngorongoro crater and plunge into the lake to find the secret entrance, not knowing that Olrik and Razul are right behind them. The four adventurers enter the sanctuary where they are quickly encircled by threatening guards, only