meets Piper McLean at the Wilderness School in Nevada. Later, in The Lost Hero, he meets Jason Grace, who wakes up on a school bus headed to the Grand Canyon with no memories. However, Leo and Piper have Mist-induced memories of meeting and becoming friends with Jason. He sometimes thinks of himself as a seventh wheel, as for the first three books of the Heroes of Olympus series, he is the only person aboard the Argo II without a significant other, though he proves no less important or skilled than the others. In The Mark of Athena, Hazel learns her former boyfriend, Sammy Valdez, was Leo's great-grandfather. Until he falls in love with Calypso, a nymph third-generation titanness, in The House of Hades, Leo flirts with almost every girl he meets to cover up his insecurities about never finding love. In The Blood of Olympus, Leo sacrifices himself to annihilate Gaia and dies in the process, but is brought back to life using the Physician's Cure and returns for Calypso on her island, Ogygia. This is an impressive feat, as nobody has ever been to Ogygia twice. However, Leo had the advantage of an astrolabe that had been created for just such a purpose by Odysseus as an old man. Leo had gotten the device from two dwarfs shortly before landing on Ogygia and had learned from them that Odysseus had lacked a vital crystal to complete the device which Leo had convinced Calypso to give him before leaving the island. He and Calypso then journey back to Camp Half-Blood, sending a magic scroll ahead to let his friends know he's alive. When he does arrive at camp (at the end of The Hidden Oracle), everyone lines up to punch him for keeping them worried for so long. As Leo is included in the prophecy of the Grove of Dodona, he and Calypso accept the task to accompany Apollo on his quests in The Dark Prophecy. Afterward, he announces that he and Calypso will be living at the Waystation and leading an ordinary life. When the prophecy of Trophonius requires that someone must warn Camp Jupiter of an invasion, Leo does the task alone. He returns, but later learns of Jason's death. In The Tower of Nero, Apollo encounters Leo briefly while visiting the Waystation after becoming a god once again. Festus Festus is a mechanical dragon made decades ago