Seemingly nothing in this world daunts the young criminal mastermind Artemis Fowl. In the fairy world, however, there is a small thing that has gotten under his skin on more than one occasion: Opal Koboi. In The Last Guardian, the evil pixie is wreaking havoc yet again. This time his arch rival has reanimated dead fairy warriors who were buried in the grounds of Fowl Manor. Their spirits have possessed Artemis's little brothers, making his siblings...

Spirits have possessed teenage genius Artemis' little brothers. Artemis has until sunrise to get the spirits to vacate his brothers and go back into the earth where they belong.

On a cross-country vacation with their parents, twins Coke and Pepsi, soon to be thirteen, fend off strange assassins as they try to come to terms with their being part of a top-secret government organization known as The Genius Files.