Pirate hunt

Tharja has a ancient journal written in a odd language handed down to her from her grandmother Ida. Ida was one of the few that had been allowed to explore the island Slymark by Efren. The group had come back with nothing officially. Ida though tells Tharja a different story as she is on her death bed. Tharja is the youngest of her family and is very young when Ida gives her the book. Tharja looks at the book for a while before putting it in a safe location and forgetting about it for several years. When Tharja becomes of age she meets Dermin. They marry. They work at a mystery solving company. After several successful missions together they run into one that brings up the legend of Ewert the mark and Claudine sly. A fire at home brings the pair back to Tharja’s home. There she remembers the book. As they both look they find it connected to the pirates. Tharja’s family is killed off by Shade. They quit the mystery company to purse this thought that it is a way to find Ewert and Claudine’s treasures. They work on the book. Book is written in an ancient language but also in code. They break code. As they read they find out that both the island Slymark and Marked sly were used. Slymark was used as a way to get to the island Marked sly which no one has set foot on in generations. Magic was used to make a portal to get to Marked sly.
As they start to go explore they are attack by Shade. They have to escape them get to the island. Shade tries to use them to get the treasure. They make it to Marked sly to find an a few shifters living on the island. They are the decedents of the crew mates of Ewert and Claudine’s. Find out that Tharja is that last living decedent of Ewert and Claudine. So the treasure belongs to her. They learn the truth behind the legend Ewert and Claudine.