Criminal mastermind Artemis Fowl is back and so is his cunning enemy from Artemis Fowl: The Arctic Incident, Opal Koboi. At the start of the fourth adventure, Artemis has returned to his unlawful ways. He's in Berlin, preparing to steal a famous impressionist painting from a German bank. He has no idea that his old rival, Opal, has escaped from prison by cloning herself. She's left her double behind in jail and, now free, is exacting her revenge on all those who put her there, including Artemis.