The Prophesied 7 have finished their quest. Leo has returned with Calypso, and peace has been restored to the demigod world. But the mortals don't know that. What do they think when our heroes show up in their world?
When the gods do not keep their promise and Calypso dies in Leo's arms for leaving the island, Leo comes back to CHB a changed person. He doesn't crack jokes anymore, he ignores his friends and isolates himself from everyone.
But most importantly, he wants to take revenge on the gods, and no one was going to get in his way.