Percy Jackson is a high-school senior who needs three letters of recommendation from the gods to secure his place at New Rome University, and the Olympians never give anything for free. Following the events of The Chalice of the Gods, Percy earns a shot at his second letter by taking on an unusual job: pet-sitting for Hecate, goddess of magic and crossroads, while she is away over Halloween week. The rules are simple. Look after her pets as if their lives depend on it, because they do, and do not touch anything, especially her magic potions. Percy, his girlfriend Annabeth Chase, and his best friend Grover Underwood move into Hecate's seemingly endless mansion and get acquainted with her two fussy, terrifying animals: Hecuba, a massive grieving hellhound, and Gale, a flatulent polecat. Predictably, things go wrong. A potion mishap wrecks the mansion and the pets escape into New York City. With only days before Hecate returns, the trio must track down the runaway animals and restore the house to order, or face the goddess's full three-headed fury. It becomes a frantic, Halloween-flavored race across the city, blending humor and action with unexpectedly tender emotional beats about responsibility, loss, and growing up. The second book of The Senior Year Adventures, it is a more intimate, lower-stakes, character-focused adventure than the world-ending earlier books, smaller in scope but emotionally deeper, with the crossroads motif of choices and consequences running throughout.