The latest in a long line of Secret Royal Guards attempts to protect the emperor not with his impressive kung-fu skills, but with a collection of impractical devices of his own creation. Each of the twelve agents is named for one of the 12 Chinese Zodiac Animals, and assigned a specific task to keep the emperor safe. Agent 00Tiger is a true martial arts master, but Agent 00Dog (Louis Koo) just isn't as strong as his physically capable counterparts. In order to compensate, Agent 00Dog begins inventing a series of whimsical security devices that often do more harm than good. When Agent 00Dog discovers that the Chief eunuch Unicorn has hatched a plot to assassinate the emperor, he vows to prove his worth once and for all by putting his oddball inventions to the ultimate test. Once the kingdom has been saved, the Empress (Sandra Ng) will have her pick of handsome suitors.