Forgotten Chest

What is hidden in a mysterious old wooden chest? Where are the keys, and why has the previous owner never returned home?? This is the front cover illustration for the mystery thriller book "The Case of the Forgotten Chest" by Julion Okram (Slovak title translation: "Prípad zabudnutej truhlice"). A pencil drawing of an ancient old wooden trunk locked with a red padlock. More: www.okram.fr