In the sixth book, "The Time Paradox", Artemis' mother Angeline Fowl becomes gravely ill with a rare fairy disease called Spelltropy. Artemis attempts to cure her with his remaining magic, but it only serves to worsen her condition. The only cure for Spelltropy is found in the brain fluid of the Silky Sifaka Lemur, the last of which Artemis sold in a business deal when he was ten years old, resulting in the extinction of the species. To get Holly to help him, Artemis falsely accuses her of exposing his mother to magic, which led to her developing the disease. Holly believes Artemis and, ridden with guilt, accompanies him to the past to rescue the last lemur from his younger self. After several misadventures, Artemis recovers the lemur but learns that his mother's illness was a ruse plotted by Opal Koboi, who wanted the lemur's brain fluid to increase her own magical powers. Artemis ruins Opal's plans by bringing his ten-year-old self into the present and fooling Opal, saving his mother in the process. Opal flees, but returns again as Artemis appears to take the lemur and fly off the manor's grounds in his Cessna. She chases him, following the thermal read of the lemur and slowly destroying the plane until it crashes on the shoreline. At the crash site, the two stand off until she discovers that the lemur is actually only a decoy, fitted with a thermal read to trick Opal. Before she can further injure Artemis, he shoots the boulder she's on, and it is shown that it was in fact the shell of a kraken she stood on, built up with gases that exploded with the pressure of Artemis's shot. The LEP team later informs Artemis that Opal's body was not recovered from the rubble. As a result of Opal meddling with her mind, Angeline Fowl learns of Artemis' contact with the People, and she asks Artemis to tell her the truth. Artemis' 10-year-old self has his mind wiped by Nº1, but retains a brief memory of the existence of fairies,