In his continuing quest to earn college recommendation letters from the gods, Percy has to pet sit the goddess Hecate's polecat and giant mastiff during Halloween week. What could possibly go wrong?

Rick Riordan’s newest Percy Jackson adventure delivers hilarious set pieces, a diverse cast of gods and monsters, and plenty of delightful tricks and treats. Percy Jackson, now a high school senior, needs three recommendation letters from the Greek gods in order to get into New Rome University. He earned his first by retrieving Ganymede’s chalice. Now the goddess Hecate has offered him another “opportunity”—all he has to do is pet sit her polecat, Gale, and mastiff, Hecuba, over Halloween week while she is away. Piece of cake, right?

Percy, Annabeth, and Grover move into Hecate’s seemingly endless mansion and start getting acquainted with the fussy, terrifying animals. The trio has been warned not to touch anything, but while Percy and Annabeth are out at school, Grover can’t resist drinking a strawberry-flavored potion in the laboratory. It transforms him into a giant frenzied goat, and after rampaging through the house, destroying everything in sight, he passes out—giving Gale and Hecuba the perfect chance to escape.

Now the friends must track down Hecate’s pets and somehow restore the house before she returns on Saturday. It’s going to take luck, demigod wiles, and the help of both old and new friends to hunt down the animals and set things right again.