Will and Nico receive a blessing from Will's father, Apollo, that gifts them with two children. Even though they were only supposed to receive one child they receive a set of twins-a boy and a girl. Life seems good and they're happy, living as normal of a life as possible being a family of demigods, which has its ups and downs. However, Will ends up going missing one day and Nico is left convinced that Will left of his own accord and changes completely, reverting back to his old self as he begins to believe once again that everyone he loves will leave him like Bianca did all those years ago. The twins, being polar opposites and rarely getting along as siblings do, are sent on a quest in order to figure out exactly what happened to Will and where he went, as they know he didn't leave by choice.