Father Rodriguez, who has looked after Esteban since he was a baby, tells him a great secret on his deathbed: somewhere his father may still be alive. So Esteban decides to begin his search in the New World. With the help of Mendoza, a mysterious man who claims to have rescued him as a baby, Esteban hides as a stowaway, aboard the Esperanza. As they are about to set sail, he meets a young Inca girl: Zia.

The two children, Esteban and Zia, find out that they both wear the same strange medallion. The Esperanza crosses the Atlantic and nears the entrance of the Straits of Magellan, where wild seas and strong winds create terrible storms. Mendoza, the navigator, prepares to spend four days and nights at the wheel.

Buffeted by a fierce wind and a wild sea, the Esperanza manages to sail through the Straits of Magellan, under Mendoza's guidance. But now, the ship faces another trial of strength: it is in the grip of a hurricane.

Esteban and his friends barely cross through the terrible Straits of Magellan before their ship, the Esperanza, sinks in a storm. Tossed around on a small raft and attacked by sharks, they're left in the middle of the ocean, with no provisions. But a seagull overhead guides them towards the closest shores, and they finally reach a small island.

After a dangerous journey, Esteban and his friends are washed up on a mysterious island. That night, a shadowy figure comes creeping towards them. Silently, the figure steals a chart and a pistol, then snatches up Zia. Esteban gives chase. He discovers a curious house in a tree, where Zia is a prisoner. To Esteban's surprise, the mysterious shadow turns out to be a friendly boy of his own age, called Tao.

On a small island among the Galapagos, Esteban and Zia find a young boy living all alone: Tao. His ancestors left a magnificent ship, the Solaris, which contains their ancient secret knowledge, hidden in a temple on the island. Esteban and Zia want to use the ship to reach the mainland.

Gomez' Spanish galleon overtakes and attacks the Solaris, the sun-powered ship on which the children are travelling. They manage to outrun the Spanish ship when Tao discovers a wonderful secret solar power boost, just in time. At last, they reach the new continent.

After many adventures, Esteban and his friends finally set foot on the new continent. But there, they meet the soldiers of Governor Pizarro, men who think only of gold. They capture Zia and try to make her tell them the way to the Cities of Gold, but Tao and Esteban help her to escape.

Esteban and his companions escape from Pizarro, but their fabulous ship, the Solaris, is taken by Gaspard and Gomez. They offer to exchange the ship for Zia, and her secret. Trying to save Zia, and the friendly Inca people in the village, Tao blows up Gomez's ship, but sadly the Solaris is also destroyed.

Esteban and his friends are on their way to Zia's village, when they are surrounded by Spanish soldiers. The children manage to escape, and take refuge in an underground temple, where they meet the old priest, Pasha. To help them escape, the priest melts the pillar of ice that supports the temple roof, and it crashes down on top of him. The others just manage to get away.

Gomez captures the children and forces Zia to reveal the secret of the Golden Quipu. It is an Inca message which reveals that the Cities of Gold lie beyond the High Mountain Peak. In the night, Esteban and the children escape. They find a secret underground passage and set off for the High Peak.

The Spanish army follow Esteban and his friends to the Fort of the Black Eagle. Under cover of darkness, the Spaniards attack the fort, but Tao devises a rocket flare that repels the attackers, saving the fort. The three children leave the fort and at last reach the City of the High Peak, whose chief, Kraka, tells them that the medallions Esteban and Zia wear can open the doors of Sela, one of the Cities of Gold.

When Esteban arrives at the place called the High Peak, he meets an old man, Mayuka, who seems to know something about his parents.

Mendoza steals the Spanish army's cannon in order to win the trust of the Indians, but his plan fails. As the three Spaniards are about to be executed, Esteban comes to save them. But he demands that Mendoza give him back the sun section of his gold medallion.

Gomez and his soldiers attack the Fort of the Black Eagle to try to recapture the cannon Mendoza had stolen. Mendoza uses the cannon to fight back, but cannot stop the Spanish army who storm the fort and drive the Incas out. Esteban, Tao and Zia run away towards the High Peak, following secret underground passages constructed by the Incas.

Searching for the Cities of Gold, Esteban and his friends cross a high plateau up in the Andes. Near Lake Titicaca, they are attacked by the Urubus, a tribe of giants. Tao invents a submarine, and they capture Karuga, chief of the tribe, and hold him prisoner. Karuga tells them that there's a City of Gold on a mountain, guarded by the earth goddess, Pachamama.

The setting sunlight leads Esteban and his friends to the statue of the earth goddess, Pachamama. The legend goes that when Pachamama takes the sun in her arms, the Gates to the Cities of Gold will open. Estaban and Zia place their medallions in the statue and the mountain opens up to reveal the first City of Gold. Inside they discover a great bird, made of solid gold.

Inside the first City of Gold, Esteban finds a great Golden Condor. When the volcano on which the Cities are built begins to erupt, the Cities are destroyed. Sheltering inside the body of the Condor, they try to make its mechanism work, using the Medallion of the Sun. Suddenly, the giant bird spreads its wings and takes flight.

The great Golden Condor, carrying Esteban and his friends away from Pachamama and the erupting volcano, lands in the desert at Nazca. But when Pizarro and his soldiers arrive, Esteban makes sure everyone escapes.

The Golden Condor carries Esteban and his companions to the High Peak, where they encounter the Spanish forces, armed with their cannon. With the help of the Golden Condor, they stop Gomez and Gaspard. And when they had saved their friends, they leave the High Peak, in search of the land of the Mayas.

The group head for the land of the Mayas, on board the Golden Condor, when they are forced to land in the jungle. They are captured by Amazon warriors and taken to their temple, to be sacrificed to the Rain God. But Esteban uses his special powers, and the sun comes out. The Queen is so impressed by his power to command the sun, that she orders their release.

Esteban and his friends on board the Golden Condor have to make a forced landing in the jungle, where they're captured by Amazon warriors who want to sacrifice them to their Rain God. After some difficulties, they manage to escape from this dangerous situation. And in the end, the Queen of the Amazons allows them to leave for the land of the Mayas.

In the jungle, Esteban and his friends discover some ruins, deserted temples and pyramids. In one of the temples, Pedro and Sancho try to remove a jade mask from the wall when the mask begins to glow. Suddenly the stone beams shoot out of the walls, ceiling and floor and trip them up.

After solving the secret of the green jade mask, Esteban and his friends find a manuscript which seems to hold the key to the whereabouts of the Cities of Gold. But almost immediately, they are captured by Doctor Fernando Laguerra and his friend, Marinche, who are also searching for the Cities of Gold. However, Kokapetl manages to rescue them all.

Esteban and his friends are captured by Indians who wanted to sacrifice them to purify their sacred lake of gold. Marinche and Doctor Laguerra try to poison the lake so they could get at all the treasure on the bottom. Mendoza foils their plan by breaking through the dam, flooding the village and allowing the children to escape.