The Opal Deception (Artemis Fowl, The Graphic Novel, Bk. 4)

Artemis Fowl's greatest enemy, the evil pixie Opal Koboi, has escaped - and she's out for revenge. Her plan to start a war between the humans and fairies is nearing completion and once again Artemis is caught in the crosshairs. Only this time he has no memory at all of his fairy friend, Captain Holly Short, or her world deep underground. To survive Opal's master plan, Artemis will have to reconnect with Holly and with his own memories. But will even Artemis's keen intellect be enough to outsmart this pixie villain, or has the boy genius finally met his match?