Dear Sir, I work at the Paris Observatory. While consulting our archives, I discovered a correspondence between my father, Mr. Cassini, and the renowned Mr. Huygens, in which was mentioned a project of the Royal Greenwich Observatory to reassess the position of the stars in the sky of the southern hemisphere. The French and the Dutch are said to have offered the British a collaboration. Unfortunately, these nations being then at war, this could not succeed. Recently, I found some documents in the desk drawer of a former colleague. These documents reveal that a secret mission would have been mounted at the time to send a French scientist to assist the British. It was agreed that a young astronomer should take part in the crew of the pirate François le Sage, then active off the Guinean coast in Africa, to discreetly join his counterpart and take part in the southern observation. This project was a failure for the French, because no news was given by their emissary. Until I came across these strange cards, signed by the hand of the missing person. From what I understand, the young astronomer would have sunk into madness, and would have converted to piracy. He would have constituted a "treasure", probably containing booty from pirate raids and concealment of thefts, which he would have buried somewhere not far from the place of scientific observation. Since then, no more news. I think these cards are genuine and lead to treasure. One of my colleagues told me about you. It seems you excel at the art of treasure hunting. If you will help me understand these maps and possibly find this treasure, I will be curious about what's in it. Jacques Cassini.