Artemis Fowl series

In his second adventure, the youngest, brightest, and most dangerous criminal mastermind is at boarding school when he receives an urgent e-mail from Russia. It's from a man Artemis never thought he'd see again: his father, who has been kidnapped by the Russian mafia and pleads for Artemis's help.

Criminal mastermind Artemis Fowl has no memory of the fairy people and his dangerous enemy, Opal Koboi escapes from jail and is planning revenge.

Artemis's mother has contracted a deadly disease -- and the only cure lies in the brain fluid of African lemurs. Unfortunately, Artemis himself was responsible for making the lemurs extinct five years ago. Now he must enlist the aid of his fairy friends to travel back in time and save them. Not only that, but he must face his deadliest foe yet...his younger self.

"Teenage genius Artemis Fowl and his arch rival Opal battle to the last in this eighth and final book in series"-- Provided by publisher.