After the capture of the Fort of the Black Eagle by the Spaniards, Mendoza destroys the suspension bridge linking the Fort to the High Peak. At the High Peak, Esteban exposes his plans to Kraka: to continue their quest for the Cities of Gold. Kraka thinks it's a far too risky quest for three single children.
At the same moment, appear Mendoza, Pedro and Sancho. Mendoza says he wants to accompany the children to the mountains of the south supposed to host Tseila, the first of the Cities of Gold. Kraka authorizes their departure, accompanied by Wayna and a small group of Inca soldiers. During the arid walk to the south, Sancho and Pedro think that Wayna should be ridded to be alone with the children. Mendoza tells them to wait for the right moment.
Suddenly, the small group makes a strange discovery: a heavy bronze arrow planted in a rock. Wayna indicates that this arrow belongs to the Urubu tribe, giant and great warriors. Also he recommends to the children and to the three Spaniards the greatest prudence. Kokapetl warns them: the Urubus are approaching! Wayna orders the children to retreat while the Incas attempt to contain the attack of the dangerous warriors. Mendoza takes the opportunity to take the children with him. They manage to hide themselves inside a crack in the mountain and emerge a few meters away. Mendoza says they can't wait for Wayna and his men, otherwise they would fall into the hands of the Urubus.
On the bend of a rock, Esteban finds a girl lying on the floor, fainting. She regains her senses and introduces herself: her name is Lana and she is said to have been kidnapped by the Urubu tribe. According to her, they have to join her village because the Urubus must be in pursuit. All set off and arrive in the evening on the shores of a lake. Lana says this is the lake of her village and she calls her family whistling in a reed stalk. Other whistles are heard in the distance. A thick mist rises and boats approach. Lana finds her father, Sabal. Esteban and his friends embark aboard the boats and join Tetola, the village of floating reeds of Lana.
But hardly have they time to enjoy a meal prepared in their honor that a villager alerts the chief. Sabal believes that the giants will attack the village early in the morning. Resigned, Lana thinks of offering herself as a sacrifice to the dangerous warriors in order to spare the people of Tetola. The dawn rises and the invention of Tao is finally ready: it is a submarine equipped with a periscope and a knife attached to the end of a pole. As expected, the Urubus assail the village on their rafts. With the help of the submarine, Esteban and Tao dismantle the raft. The giants fall in the water and think they are dealing with the "lake monster". They flee and only their chief, Karuga, is captured. He explains that the girls from the lake were kidnapped to satisfy the goddess Pachamama. If Pachamama wasn't satisfied, she poured out her anger as well as the "sacred fire" from the top of her mountain. Tao remembers the indication given by Kraka at the High Peak: it is this same goddess, Pachamama, who keeps the entrance of the Cities of Gold.
Esteban then asks Karuga where is the mountain of the goddess. The giant points to a mountain in the distance, "the mountain of the Cities of Gold" ...