Nimona is a young shapeshifter, the sidekick to the Lord Ballister Blackheart, who is a villain with a vendetta. Blackheart wants to prove that Sir Ambrosius Goldenloin and his allies at the Institution of Law Enforcement and Heroics aren't the heroes they say they are. In the beginning there are small acts of mischief, which escalate into explosions, with science and sharks in between.