Nico di Angelo is still on the process of moving on and finding his feeling for the son of Apollo when the spirit of the oracle issued him on a quest to search for her.
Will Solace likes having Nico around. But when the Zeus locked Apollo up(no more Haiku!) and Hermes was delivered to send him to lead a quest with no prophecies to guide him, things could just get any worse.
Leo was thought by everyone as dead. Though he's just flying through the sky on Festus with his lady. Apparently, he and Calypso seems lost, not even the gps helping them, circling the perimeters of Ogygia. The gods aren't making his happily ever after easy.
Togther they should defeat an ancient monster only Apollo could kill, which is easy if the Sun God was only around.