The Count of Champignac is on a treasure hunt in Australia. One night he sleeps near a cave, where Aborigines live, and two criminals have a mind to steal a diamond-studded skull. One of the diamonds falls in the shoe of the Count. Spirou and Fantasio join the Count in Australia. When they arrive in Australia, they meet Jessica, who sniffs out a chance for a good story. In the meantime, the Count is caught by two criminals. They don't know anything about the diamond in his shoe, but they think that he has found a treasure from the Aborigines. Kalulong, one of the oldest Aborigines, sees with his spiritual powers that the holy stone is back in the cave. The Aborigines go there, where the Count is held by the criminals. Spirou and Spip are on the way there as well to save the Count.
—Anonymous