The Seven Crystal Balls
Professor Hercules Tarragon hosts a mysterious evening for Tintin and his friends in "The Seven Crystal Balls". He was one of the Sanders-Hardiman expedition members and displays the mummy of Rascar Capac in his home. He had previously been a classmate of Professor Calculus and this connection enables Calculus, Tintin and Captain Haddock to visit him at home one evening while he is under heavy guard during a summer rainstorm.