Catrina has a secret: she can fly when she says, 'Peas make me sneeze.' She calls herself Catastrophe Girl because she can fix catastrophes and her secret name is similar to her own name.

Today, Aunt Lily, who is a tap dance star in the musical Starlight, has come to stay. She is Catrina's favourite aunt because she has a secret too: Aunt Lily can stand on her hands and walk around upside down. She brings five kittens for Catrina’s birthday but as soon as the kittens are named and put to bed, they disappear.

Catrina and her friends Alexa, Zoe, Roy and Sam search for clues, but something bigger is happening in Crickle Marsh: Aunt Lily’s friend Rita has had her 10 million-dollar necklaces stolen. Catrina and her friends follow the clues to a farmhouse where they hide. As the thieves drive away with the kittens, the friends try to follow.

Catrina becomes Catastrophe Girl but her magic won't work – something is wrong. She has to solve this before she can go after the thieves. Constable Cecil Stout suspects several people but can't arrest them as he has no proof, until Catrina and friends tell him about Pearly Pickleman and the cruise ship. It is then that Aunt Lily is captured and Constable Stout, who has a crush on Aunt Lily, must first find her before he can go after the thieves.

In a lucky break, Aunt Lily’s tapping saves her, and they all search for the thieves Pearly, Percy, Curly and Scrog. The police are waiting. But no one knows how the thieves will get the necklaces past the security of the cruise ship as well as past Constable Stout. Then, Catastrophe Girl hears a vital clue and uses her magic powers to find the kittens and the necklaces before the ship sails. Just when Constable Stout thinks he has discovered all the necklaces he is foiled. Where are they hidden? It is up to Catrina's quick thinking and Aunt Lily's tap dancing to get them back.

The thieves are taken to gaol and everyone is happy, except the friends who know there is still one missing necklace and one missing thief. Who could it be? Where is the necklace? At the opening of Aunt Lily's musical show, Catrina discovers where the last necklace is and who the thief is. But the guards at the show Starlight won’t let Catrina and her friends into the actors’ dressing rooms so they can expose the last thief. Aunt Lily, seeing the problem, uses her own secret handstand to distract the guards and help them.

At the last minute, Catrina says her magic words 'peas make me sneeze', becomes Catastrophe Girl, and uses her powers to captures the thief. The musical is a success. Catrina asks Aunt Lily if she is sorry that people know about her secret now. Aunt Lily says it is better to help a friend than keep a secret. Aunt Lily and Constable Stout have a date, the friends are happy, and Catastrophe Girl still has her secret powers.