Mister O'Lui and Rupert can't believe their eyes: First, the flower bed is devastated, then their picnic is plundered, and finally, the pear tree is stripped bare. Rupert is convinced that a monster is causing all this trouble! But Mister O'Lui has his doubts. Could it be that Rupert is just trying to distract him because he himself devoured the picnic? Brave Rupert sets off without Mister O'Lui to get to the bottom of the matter, while Mister O'Lui is plagued by guilt: Perhaps he made a mistake and wrongfully suspected his best friend. Can Mister O'Lui not only find the true thief but also muster the courage to apologize to Rupert?.