Tom was a bright boy who loved detective stories. During summer vacation, he spent a week with his cousin Paul in the countryside. One morning, the boys found a mysterious letter in the mailbox.

The letter only contained a series of strange symbols. “It's a secret code!” Tom cried excitedly. “Let's crack it!”

The boys set to work. They tried out different codes, compared the symbols with letters and looked for patterns. After hours of pondering, they had an idea: The symbols stood for numbers, which in turn represented letters in the alphabet!

They slowly deciphered the message: “Follow the old oak tree to the treasure.” Tom and Paul looked at each other wide-eyed. A real treasure?

They ran to the oldest tree in the garden - a gnarled oak tree. At the foot of the tree, they discovered a spot where the soil was freshly agitated. They dug around and actually found a small wooden box!

In the box was a photo of Tom and Paul's grandfather as a young man, together with an old pocket watch. A note explained that this was a family heirloom that he had hidden for his grandchildren.

Tom and Paul were over the moon about their discovery. They had not only broken an exciting code, but also discovered a valuable memento of their grandfather. It was their biggest detective adventure yet!