Mo travels to Hong Kong to shoot her movie and unexpectedly comes across another ancient book of martial arts secrets in this fast-paced, high-kicking sequel to The Legendary Mo Seto. 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, along with Mo's Dad, are whisked away to Hong Kong to start work on The Protege. 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 in the Kwok family's fancy penthouse apartment, where Mo and Dax meet Cody's fifteen-year-old sister, Fiona, who's full of natural martial arts talent. Mo is shocked when Cody's father gifts Fiona a very familiar book: the Book of Sorrow, a piece in the trilogy of books that hold ancient techniques that have been passed down for generations. How did Cody's family get it? With Mo's dad's attention diverted to seeking the truth about the Five Claws, Fiona offers to show Mo around Hong Kong. As their friendship grows deeper, Fiona teaches Mo techniques from the Book of Sorrow in between filming.

But it turns out Fiona has ulterior motives, and soon, Mo finds herself taking on the Five Claw Society once again, this time with the help of Dax, Cody, and her best friend, Nacho. Can she protect the book and make her martial arts dreams come true?