"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 one by retrieving Ganymede’s chalice. Now the goddess Hecate has offered Percy 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 settle into Hecate’s seemingly...