Percy Jackson and his friends are back at Camp Half-Blood after the war with the Titans and they're hoping for a quiet Summer. Well, as quiet as it can be when you're a Demigod. However, when Chiron calls for an emergency meeting with the Campers, they find that this Summer is going to be just as action packed as the last 4 as they're sent to New York following reports of a rise in Monster activity. Meanwhile for the Shadowhunters of the New York Institute, things are getting dangerous and strange as creatures that they have never believed to be real start roaming the streets...