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?

From Beijing to the Great Wall, from Xi'an to Shanghai, the children discover the cultural riches of the Middle Kingdom. But during their journey, Hugo, Amytis and Romain discover strange tiger statuettes that attract the attention of shady individuals. And so begins a new high-risk investigation by Alain Surget.

Going on an adventure to Russia, the class of Alex Moury starts a long journey to Irkutsk on board the famous Trans-Siberian. But, through their different stops to visit monuments and dive into the history of the country and regions they visit, the children notice a spy follows them. More precisely, follows Alex Moury. Why? Would the teacher hide a secret? Is he in danger?