Meztli and Cualli are rescued from a Inca human sacrificial site where virgins are left to die to appease their gods after conquistadors invade their lands. Zolin, Meztli's childhood friend has been sent by Hermit Tupac to rescue them, which he does.
They now must follow a perilous journey along ancient Inca trails through the mountains to interior lands and Inca towns.
Etalpalli, one of the seven priests who brought the virgins to the sacrificial site has an agenda with loyalty to nobody but himself. He murders the six other priests who accompanied him to the site and on learning that two of the three virgins are still alive attempts to find them.
Conquistador Capitán Buena Giraldo, commander of the sector of the Inca empire where Meztli and her friends live has more interest than just converting locals from their heathen ways. He wants to find a rumoured lost gold mine in the area. He teams up with Etalpalli who lies about his knowledge of where the mine is when really his aim is to find Meztli to enslave.
On their way to the east, Meztli and her two friends are met at a junction in the trail by Urco, from Cualli's village. He has been sent by Tupac to tell them that all the lands have been conquered by the conquistadors and there is no safe haven through the mountains. Instead they must follow the strings and knots, that Incas use to communicate instead of a written language, to a secret cave that goes under the mountains to a hidden valley and golden pyramid. There they would be safe.
But are they?
A far greater threat catches up with them. It is smallpox, a plague brought by the conquistadors that is devastating the local population. Only a few adults survive. For some unknown reason the conquistadors are immune and Inca children also have a high survival rate.
After travelling through the cave, Meztli and her friends arrive in the secret valley of Ehuraythak and golden pyramid to find that the entire population of adults have died from the plague and only children have survived. These are lead by two twelve-year-olds, Palia and Ekko who soon welcome the four adults and the tiny community becomes self-sufficient.
Meanwhile, Tupac learns that a new order of fanatical priests have arrived to replace the original ones in the local temple who died with the plague. Their solution is to sacrifice all the children and the few remaining mothers at the next full moon. Tupac is too old to be able to stop this latest sacrifice himself so sets out to find Zolin, Urco and the maidens to return to the sacrificial site and rescue the latest victims.
On the way he is attacked, not by the conquistadors but by rogue priests including Etalpalli. His llama is killed and he is shot by a musket that the conquistadors have brought to their land but manages to fight them off by using his slingshot. His one thought now is to get to the pyramid but with a musket ball in his shoulder he is weak and knows that if the ball is not removed he will die. Only sheer willpower keeps him going through the cave.
Back at Ehuraythak, Palia and Ekko notice someone coming down the trail. They alert Meztli and Tupac is rescued. Though extremely weak he survives and tells the four that they must return to the sacrificial site to rescue the mothers and children before the next full moon that is now only two weeks away.
Meztli and her friends begin a new journey back with a race against time through hostile territory controlled by the conquistadors and rogue priests. Their success depends on the help of others and sometimes the enemy become almost friends. The cost, though is gold and a lost gold mine that Capitán Giraldo believes is still in the area.
Does this mean that the pyramid at Ehuraythak must be surrendered or is there another gold mine somewhere?
Do they reach the forty children and adults about to be sacrificed in time?
All will be revealed in this Ancient Ancestors latest novel.