A new day is rising on the Andes. Commander Gomez's troop is angry with the flight of the children. They'd like to find a guide to go with them through the dark Inca valleys. This is the moment that choose Mendoza, Pedro and Sancho to re-appear and offer their help to the Spaniards, to take advantage of the situation to find the children!
A few kilometers away, Esteban, Zia and Tao accompanied by Wayna and Ketcha, the two messengers of the High Peak, continue their ascent to the great Inca city. The Spaniards quickly catch them up. The children flee once more and have to climb a cliff at the top of which they end up on a ridge. There, lies the Fort of the Black Eagle, vanguard of the High Peak City. The children go there and meet Upanki, leader of the fortress. The Spaniards also arrive at the gates of the Fort of the Black Eagle, but Gomez prefers to charge Mendoza to prepare an attack , rather than go headlong as Gaspard suggests.
Inside the fort, the Inca troops are preparing to defend their city when Mendoza comes to meet Esteban. The tension rises but Esteban begs Upanki to let Mendoza talk to him. The latter greets the boy and sends him a sign: "See you soon! Maybe even tonight!" Esteban then understands the message of Mendoza: the Spaniards will launch an attack on the fort at night.
Indeed, Gomez and his men attack at night and thanks to an invention of Tao, the Incas win the battle. The next day, Wayna and Ketcha accompany the children for the last kilometers separating them from the High Peak. Behind a waterfall, the children enter a cave in the bottom of which sparkles a light. Dazzled, the children discover the marvelous Inca city of High Peak, perched in the clouds under the Machu Picchu. Wayna and Ketcha present Esteban, Zia and Tao to Kraka, the chief of the High Peak, under the fascinated eye of the inhabitants of the city. Kraka soon notices the medallions worn by Zia and Esteban: the two children learn that they are in possession of the keys that will open the doors of the City of Gold of Tseila ...