In the seventh book, "The Atlantis Complex", Artemis contracts a mental disease called Atlantis Complex disease, similar to OCD, and now has an alter-ego named Orion, who is in love with Holly Short, and has a strange fascination with bivouacking. Due to the disease, Artemis finds himself obsessed with the number 5 and fearing the number 4 (which in Chinese sounds like the word for death). The disease worsens throughout the novel, leading to his distrust of close friends. A neutrino shock from Holly Short frees Artemis' alter-ego Orion but he comes back after being knocked out by a buzz baton blow from Holly. He later undergoes Atlantis Complex Disease treatment by the fairies, curing him and restoring his former self.