With Tao as a hostage, the Olmecs force Esteban and Zia to use their medallions to open the doors to the City of Gold.

The Olmecs place the Sun Power Unit at the bottom of their sunlight collecting crystal and activate it. However, the unit does not behave as expected and the Sun Power Unit begins to overheat. The High Priest of the Cities of Gold, who turns out to be Esteban's father, tries to shut it down using Tao's jar which is actually a control unit. But he could be too late.

After much travelling and many adventures, Esteban and his friends finally discover the third temple built deep inside an enormous cave. A golden statue is holding a third manuscript which mentions a mountain known as "The Burning Shield".

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.

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.

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.

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.

Having found the Burning Shield, Esteban and his friends fall into the hands of the mysterious Olmecs, who possess very advanced technology. They escape from them, but are captured again. So what will happen to them now?

In the Indian Village of the New Sun, Zia at last finds her father, Papacamayo. But her happiness is short-lived, when he dies from his wounds, after defending the village against an attack by the Olmecs. All the Mayan tribes unite to fight against the Olmecs.

Esteban and his friends manage to find their way into the Olmec base. But Kalmec discovers them, and takes Zia prisoner. Suddenly, a gigantic war machine rushes up from deep inside the Olmec underground temple.

After wounding the High Priest of the Cities of Gold, Kalmec steals the Great Treasure, a concentrated source of the sun's power also called the Sun Power Unit. However, the security systems of the City are activated and destroy the Olmecs' flying machine. Kalmec and Menator make their way back to their base, taking the Great Treasure with them.

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.

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.

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.

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.

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.

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.

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.

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.

Using their advanced technology, the Olmecs are able to collect energy from the heat of the sun, and from deep inside the Earth. They capture Esteban, Tao and Zia, intent on transplanting their cells to regenerate their elders, so they can become young again. With Mendoza's help, the children manage to escape.

The Mayan people arm themselves and attack the Olmecs, who have been tyrannising them for years. A fierce battle takes place near the entrance to the Olmec base. From the Golden Condor, Esteban and the other children bombard the Olmecs with stones, turning the tide of the battle in favour of the Mayas.