El caso de la fiesta de disfraces (Los cazamisterios, 11)

When their parents aren't around, strange things always happen to Ulysses, Nora, and Bruno Misterio. Very, very strange things. Luckily, they have Bobo, a talking dog whose nose squeaks when he finds a clue! In search of the League of Villains, the Mystery Hunters arrive in a town celebrating Halloween… with a huge costume contest! There, they encounter another very mysterious case: the theft of Trini Triunfos's costume, which has won the trophy for years… Who could be behind the theft?