"The House of Hades" is the penultimate book in "The Heroes of Olympus" series. It features Jason Grace, Piper McLean, Leo Valdez, Hazel Levesque, Frank Zhang, and Nico di Angelo as they continue to set sail towards Greece with the rescue of Percy Jackson and Annabeth Chase, both of whom have fallen to Tartarus in the previous book's epilogue, in mind; the latter couple in turn also try to find their own way out of the hellish realm. Reintroduces Calypso. The book was released on October 8, 2013.