Rupert and Ottoline find a merry-go-round that has been abandoned on the common, and restore it to its former grandeur. After The Sage of Um accidentally brings the wooden characters to life, the kids find they must rescue the enchanted carousel from the evil Thogmort who wants it for his own financial gain.
When Rupert is falsely accused, caught and tried by King Neptune's undersea court for kidnapping his prized Whistle Fish, it's up to Rupert and a little mermaid, Marina, to race against time and save the Fish, demonstrating that creatures of the land and sea must work together for the benefit of all.
Rupert's unsuccessful attempts to teach a cantankerous wood troll the meaning of friendship only causes problems for the Imps of Spring, hard pressed to bring spring to Nutwood on time. Only when Rupert allows their Wand of Spring to be destroyed in order to save the troll from his own mischief does the troll finally understand what being a friend is all about.
Rupert loses his battle to break an age-old tradition when his attempts to kindle a friendship between a knight and a fire-breathing dragon ultimately end up with them engaged in a duel to the death. Only afterward does Rupert realize that the fight was staged and now, having done what was traditionally expected of them, the dragon and knight can co-exist as friends
Rupert chooses to work around his friend, Officer Growler, and the laws he represents in order to free a rare baby abominable snowman from the influential Sir Jasper and Scrogg. However, it's only when he plays by Growler's rules is he able to help his new friend and understand that, although it might seem slow, the law is fair and just and does punish the wrongdoers.
When Rupert and Podgy find what appear to be purple cakes in the forest, Podgy ignores Rupert's warnings and eats them. Too late, he discovers that they are The Professor's creations, devised to make things lighter than air. In danger of floating helplessly into space (as well as being pestered by a Cockney-accented seagull for his snacks), Podgy is saved by Rupert and learns never to eat anything unless you know exactly what it is and where it came from.