After rescuing her dad, martial arts film star Cody Kwok, and the ancient Book of Joy from a big player in the notorious Five Claw crime organization, Mo is on to her next challenge: filming a movie with Cody! Mo and Dax are whisked away to Hong Kong to start work on The Protégés. It's Mo's first overseas trip, and she is awestruck by the glitz and glamour of the international film experience.

Soon after they arrive, they attend a party at Cody's house, where Mo and Dax meet Cody's younger sister, Fiona, who appears snobby and cold. Mo is shocked when Cody's father gives Cody a familiar-looking book: the Book of Sorrow, a piece in the trilogy of books that holds ancient techniques that have been passed down for generations. She is even more shocked when a thief steals it while the party is in full swing and not even her martial arts skills can stop them!

With no leads on the identity of the mysterious thief, Mo recruits the help of a reluctant Fiona, dons her detective hat, and, in between filming, sets out on a mission to find her ancient ancestors' Book of Sorrow. Can she find and protect the book and make her martial arts movie dreams come true?