So, sometimes really bad things happen and, for reasons that are rather complicated, you're the only one who can stop them. And sometimes, in order to do so, you have to sneak out of the house late at night to get to the Underworld. And on those occasions, you, because you are a conscientious person, leave your parents a note explaining that you know what's making everyone sick and you have to go save the world. Helpfully, you also tell them you love them and not to worry.
The problem is, your parents don't really listen to this last part, and when you finally get back the next morning . . . after Philonecron tried to throw you in the Styx, a few monsters tried to eat you, you met up with the Lord of the Underworld, and a whole shadow army tried to bring his palace down on your head--well, you find out that they have, in fact, worried. A lot.
That's from the second book, The Siren Song, when we discover that after Charlotte and her cousin Zee successfully save the world from the evil Philonecron (who is stealing children's shadows to create an army to defeat Hades), her parents ground her forever.
Yes, this is another book using Greek mythology in a modern setting. The difference between The Chronus Chronicles and the Percy Jackson series is that Charlotte and Zee are not demigods. They don't suddenly develop magical powers, and when they get thrown into the world of myth they have to defeat the bad guys with courage, luck, and stubbornness. And their parents don't understand. The plots are fairly original, the mythological people are fun (Poseidon sails around the Mediterranean on a very tacky luxury yacht), and there's enough action and adventure to keep the pages turning, but what I loved about these books was how convincing the main characters were. Plus the voice: loved the voice. (But then I'm a sucker for snarky humour.)
These books are like chocolate- and peanut butter- covered pretzels: sweet and salty and addictive. Worth being better known. Now I have to convince my library to get the third book.