All is calm at the headquarters of the Three Musketeers. Much too calm, in fact, for the taste of young detectives, who are starting to get bored. But when Uncle Geo calls from Petit-Rocher to tell them that the legendary ghost ship is back in Chaleur Bay, it's all about the action. Without the help of Professor Jarnigoine, who left without leaving skill, the friends embark on an adventure that becomes more complicated at every turn. How to explain that the inhabitants of Petit-Rocher began to hear voices? Who is this mysterious pirate everyone is talking about, but very few have encountered in the flesh? What secret lies behind the gates of Chalumott, a state-of-the-art factory that is supposed to produce clean energy, but which is guarded as a royal palace? How is it that its enigmatic owner stays permanently on his luxurious yacht? And, if that weren't enough, why are two sinister individuals constantly watching the young detectives' whereabouts? The Three Musketeers will have to be imaginative and daring like never before to unravel the mystery of the Petit-Rocher ghost ship.