Watch Hidden Track for Free: How to Stream the Movie Online at 123Movies. . Pu Pu is dumped by her boyfriend whom she loves. Before she moves out, she asks to listen to "their song" just one more time, that is the hidden track by Jay Chou. Then she leaves him and goes to her sister's place in Hong Kong. All the while she is there, she searches for the same song, the "hidden track", and from this it leads her onto a journey of discovering love and a new beginning. Despite the whole movie revolving around Jay Chou's song, Jay Chou plays only a cameo part.