Back in Gorom-Gorom, Kwamé reviews the situation: the broken talisman, the files in the electronic notebook, the visit to Tondiédo, the aunt's prophecy. Everything indicates that Professor Omar is the wise man who would know how to make the dessert green again.

But who has the other half of the talisman: Omar or his kidnappers? How to find them? When Natalie comes, she explains she works for the police! Friend or enemy? Kwamé hesitates...

The night has fallen over Tondiédo. Kwamé takes a room at the "Hôtel des Nomades" at Markoye, a nearby village. Next morning, at breakfast, he falls for Nathalie, a charming French girl, originated from Nigeria. She arranges to meet him the next day at the cyber-cafe in Gorom-Gorom. But why does she ask all these questions?

At Tondiédo, the prehistoric engravings show that once upon a time, the desert was green. Kwamé meets Clément, the guide, who knew Omar well. Can he help him to find Omar, so that the desert becomes green again?

This reminds Kwamé of a tale his aunt used to tell: ‘One day, a man will come. He will breathe life back into the grass and the trees you once knew.’

Who has kidnapped Professor Omar? Was he on the point of succeeding in his research to make the Sahara green again?

In the electronic notebook that Kwamé has found, Omar has left quite a lot of information about the prehistoric site at Tondiédo. Kwamé decides to go there, but his motorbike breaks down and he has to get it repaired by the mechanic.