After defeating Gaea, Greeks and Romans are looking forward to settling down. However, they live in a mythological world, so now the eight demigods- Jason Grace, Piper McLean, Percy Jackson, Annabeth Chase, Frank Zhang, Leo Valdez, Hazel Levesque, and Reyna Ramírez-Arellano set sail again aboard the rebuilt Argo II, journeying to stop their most formidable foe yet.