The book speaks about an incident 20 years ago. Klaus was in his best years and part of the crew of a pirate ship. They got hold of a big fish-a Venorean trader which was packed with gold, gems, finest cloth and the finest weapons and armor you can get in the whole lands of Tibia.
Pirates as they were everyone wanted the lion's share of the treasure and there was a mutiny. Klaus wrote in his diary about an unspeakable slaughtering which ended when only four of the whole crew were left. They knew they wouldn't be able to navigate the ship with less then 4 people so they made a agreement. They hid the treasure at a safe spot, made a map which was cut into four pieces. Everyone of them got one piece of the map and was told to secure the treasure with a trap...a riddle...that only he knows.
The names of the surviving pirates were: Nutty Jack, Rapp Scallion, Captain Nathaniel and of course, Klaus.
Part of the Treasure Hunt Quest.