In the solemn palace, twelve secret agents named after their zodiac signs shoulder the heavy responsibility of protecting the emperor. Among them, Gao Tianjiu, nicknamed "Lingling Dog" (played by Louis Koo), is an inventor with a head full of whimsical ideas. He repeatedly made great achievements in the process of protecting the emperor with various "magic weapons", but the reaction of "Lingling Dog" to his charming but skilled fiancée Mei Xiwang (played by Big S) was quite dull. In order to make this "Lingling Dog" a papaya, Mei Xiwang came up with a way to test "Lingling Dog". It is difficult to distinguish between loyalty and treachery in the deep palace, and murderous intentions are hidden. Around the issue of the princess's selection of a consort, various forces secretly colluded in an attempt to seize power and usurp the throne and eliminate the secret agents headed by "Lingling Dog". The safety of the emperor was threatened, and the twelve agents faced unprecedented challenges.