In this book, Werber deals with the origins of humankind through two new characters, Isidore Katzenberg and Lucrèce Nemrod.

He puts forward an alternative and surprising idea for the transitional fossil in the evolution of humanity, also called the Missing Link theory.

The plot takes place mainly in the present, when Professor Adjemian, a palaeontogist, is murdered.

Isodore and Lucrèce leave for Africa in order to uncover a secret for which some people are ready to kill.

The suspense is very intense until it reaches the last word of the book which reveals the identity of the Missing Link.