As part of a study on pre-Columbian peoples, Alex Moury's class travels to Mexico to visit Mayan country. But during a trip by canoe, some of the pupils get lost in the jungle. Fleeing from a gang of traffickers, the children take refuge with the Lacandon people. But among other dangers, the jaguar lurks. During an outing with the Indian children, the Year 6 pupils feel as if the jungle is hunting them. They flee and, to escape their pursuers, both wild animals and traffickers, they rush into a deep cave that leads to a Mayan city in perfect condition. And inhabited! To preserve their secret, will the Mayans let the children leave?