Artemis Fowl: The Time Paradox (now Artemis Fowl and the Time Paradox) is the sixth book in the Artemis Fowl series. The release date for the UK is set for 10th June, 2008; the US version was released on 7th August, 2008.In Colfer's video blogs, he mentions the book saying it may not be the last, but the last one for at least 3 years.
Angeline Fowl, Artemis Fowl II's mother, contracts a debilitating disease which Artemis cannot heal with his magic (stolen in Artemis Fowl: The Lost Colony). When Captain Holly Short and N˚1 arrive, they identify it as Spelltropy, a fairy disease that can only be cured by the brain fluid of the silky sifaka lemur. However, the lemur is extinct, as Artemis sold it to a group called the "Extinctionists" seven years previously. He tricks Holly into believing she is responsible for Angeline's disease (he believes he infected his mother), and N˚1 sends Artemis and Holly back in time for three days.
Artemis and Holly arrive eight years earlier, finding that they have changed during the travel: Artemis appeared to have aged whereas Holly was returned to her adolescence. They are discovered and captured by Butler, who locks them in the trunk of a car. With the help of Mulch Diggums, they escape and break into the compound housing the lemur, and Artemis is injured by an enraged gorilla. When Holly rescues him, she, in her new adolescence, kisses him, though she later regrets her actions. Artemis manages to attract the lemur, but is forced to release it when his younger self, also there, threatens to kill it. His younger self then flies to Morocco to sell the lemur to Dr. Damon Kronski, leader of the Extinctionists. The older Artemis and Holly manage to intercept the lemur, but eventually Holly is captured, and sold to Kronski in place of the lemur by the 10-year-old Artemis.
Kronski plans to kill Holly at the Annual Extinctionist banquet. Artemis manages to save her, but in the chaos he is thrown into a pit of fire. However, the flames are holographic. Holly, escaping, realizes that Kronski has been mesmerized. Artemis, upon waking, tries to escape but is intercepted by Opal Koboi and her minions, who have been harvesting animals for their brain fluids which Opal has been using to enhance her own magic. She also says that she has mesmerized Kronski to bring her the silky sifaka lemur which will give her the ability to control time. When he releases all the caged animals, Artemis manages to escape. Mulch, Holly, and Artemis fly by stolen shuttle to Fowl Manor, but are followed by Koboi. Upon being intercepted by his younger counterpart, Artemis reveals his identity. Mulch is captured by Opal, who sucks the information from his mind, leaving him no memory of the past few days. Holly and Artemis return to the present with the lemur, whom they have named Jayjay. Artemis, going to administer the cure to his mother, finds that Koboi has possessed his mother and also caused the sickness in the first place.
Holly and N˚1 are disabled by a mesmerized Butler. Artemis runs from Opal (who is possessing his mother's body). When she catches him, he tells her he is the Artemis from the past and the Artemis from the present is free. Older Artemis (who has snuck into the secuity booth while Opal was distracted), tranquilizes Opal's real body. Holly and N˚1 are freed. However, Opal recovers quickly, and chases the older Artemis, who is fleeing in a family airplane. Opal attacks the airplane, and Artemis is forced to land. However, Artemis tricks Opal, and she is buried in an explosion. Artemis returns home to debrief the others and finds that his mother knows everything that happened to her. Artemis realizes that if he hadn't gone back in time, Opal would not have followed him and possessed his mother, and none of his adventures with the fairies would have happened. The newly appointed LEPrecon Commander Trouble Kelp is digging Koboi out of the rubble when he discovers that she has vanished. The 10-year-old Artemis has a mind wipe spell put into his eyes so that he will not remember what happened and that when he goes back in time the past Butler will also be wiped. He is then is sent back in time by N˚1, but vaguely remembers something to do with fairies, prompting his actions which occurred in the first book.