The mist is gone because of Hecate's weak state and everyone is freaking out, the gods are going around schools, explaining the world of modern Greek mythology, different Greek-related lessons are being added to average school curriculums, and the demigods, well, they are going to high school. Yay! (A/N Note the sarcasm) The mortals are conflicted: Can they accept this new reality, or completely reject it. The only hope for the return of the Mist is a daughter of Athena and a descendant of Hecate: Dark, gloomy, shy, silent, intelligent, skilled, SUPER athletic, Willow.
Please read the story of Willow and her mentors: Hazel for Misty stuff, Annabeth to learn(But she doesn't have much left to learn), and Percy for fighting all while juggling high school and ugh, mortals. Also, don'T leave out the other seven!
Disclaimer: I am a girl and not Rick Riordan. He owns all the Percy Jackson characters. This goes for the entire book because I'm too lazy. Hehe! Enjoy!