The House of hades the fourth book in the heroes of Olympus series, was released on October 8, 2013.
At the conclusion of the previous book in the series, The Mark of Athena, Annabeth Chase and Percy Jackson fall into a pit leading to Tartarus. The protagonists are on a quest to close the Doors of Death, rescue Annabeth and Percy from Tartarus, and stop the Roman demigods from Camp Jupiter from attacking Camp Half-blood
The narrators of this book are Percy, Annabeth, Hazel Levesque, Leo Valdez, Frank Zhang, Jason Grace and Piper McLean; of the eight demigod protagonists, only Nico di Angelo does not act as a narrator.