Wow! Agree, it’s not every day that you find encrypted messages in your mailbox! And their sender is unknown... Leshka and Tolik have already received several of them - one of the mysterious drawings depicted a house, another a park, the third an oak tree, and the fourth... of course, the place where the treasure was hidden was marked with a cross! Without thinking any more, the guys rushed to find the oak tree and dig up the treasure whose location the unknown person wanted to tell them about. But what secret does the ancient oak hide? And who needed Leshka and Tolik to reveal this secret?..