During the investigation of a rock sample from the depths of Antarctica, Nastasia Wardinska uncovers traces of an ancient civilization, a civilization that is 350 million years old. Professor Mortimer immediately sets out to find further clues that ultimately point to Africa. Together with the young Nastasia and his old friend Sarah Summertown, he embarks on an expedition to Tanganyika, where an incredible discovery awaits the research team. However, they are not the only ones after this secret. An old enemy of Blake and Mortimer has a hand in the matter. But is he really who he claims to be?.