The story takes place in Tai Hom Village, a small Hong Kong shantytown that is literally and figuratively overshadowed by a large apartment and mall complex called Plaza Hollywood. The movie begins with pig butcher, Mr. Chu (Glen Chin) and his sons, Tiny (Leung Sze Ping) and Ming (Ho Sai Man) who are all obese. Keung (Won You Nam), also a resident of the town, is preoccupied with internet porn which leads him to meet Mainland Chinese prostitute Hung Hung (Zhou Xun), who advertises her services online and whom he pays for a night of torrid sex in the bushes outside Plaza Hollywood.
Johnny Du Kei-Fung (Wong Cho-Lam) is a Hong Kong detective who dreams of becoming a member of the exclusive G4 Team that protects the city's Chief Executive (Patrick Dunn). Johnny is deemed too short for the team and his application is denied. At home, Johnny is bullied by his girlfriend Angel (Kimmy Tong) as weak and unsuccessful.
As Lunar New Year 2012 marks the year of the Dragon, the film explores the Chinese's age-old obsession with the Dragon and having children on a "Dragon year" (see Chinese zodiac). In the introduction, Ah Long (Melvin Sia) tells about how his father (Zheng Geping) was desperate to have a son born in the Dragon year because his ancestors had decreed that only a "Dragon boy" could take over family's lion dance association. His mother (younger, Pan Lingling and older, Lai Meng) instead gives birth to "Dragon girls" while Ah Long himself was born several seconds after the clock struck twelve, making him a "Snake baby", much to the disappointment of his father.
Hong Deok-Ja continues to run a kimchi food company and leaves for Japan on a business trip with three sons. However when bank robbers steals their money, the family is separated from their guide,and a misunderstanding between language barriers makes the White Tiger family think that they are wanted by the cops.
For the past two years, while on suspension for adultery with a police chief's wife, detective Kang Seon-woo (Park Hee-soon), has been running a private-eye agency specializing in adultery cases. He's also being sued for divorce by his wife, Hye-young (Cha Soo-yeon). A couple of days before resuming his old job, Seon-u accepts a case from a woman, Kim Soo-jin (Yoon Jae), who wears a particularly alluring perfume. She says her husband, casino billionaire Nam Yeong-gil (Jo Won-hee), is conducting an affair with another woman at a love hotel in Gapyeong, Gyeonggi Province, outside Seoul. Seon-woo checks into an adjoining room in the unmanned hotel and is met there by Soo-jin. Instead of immediately surprising the lovers, Soo-jin invites Seon-woo to a drink and seduces him. Seon-woo wakes up next to her dead body, and in the next room finds the husband also dead. The woman there says her name is also Kim Soo-jin (Park Si-yeon) and the dead man is her husband. Along with his idiot assistant, ex-con Gi-poong (Lee Kwang-soo), Seon-woo cleans the crime scenes and buries the bodies, realizing he's been framed for the double murder. Resuming his job at Jonggu Police Station, Seon-woo investigates the case along with two colleagues: the stubbornly procedural Seo (Kim Jung-tae), who dislikes him, and the easy-going Han Gil-ro (Joo Sang-wook), who admires him. Seon-woo has noticed that Soo-jin wears the same perfume as her dead namesake, and she admits she wanted a divorce from her husband, who used to beat her. Seon-woo questions the dead Soo-jin's boyfriend, gym trainer Lee Jin-guk (Kim Yun-seong), but the trail leads nowhere. As the terrier-like Seo comes up with more evidence that could eventually implicate Seon-woo in the murders, Seon-woo finds himself falling hard for Soo-jin and on a deadline to solve the mystery.
Section chief Kim (Kim Myung-min) was dispatched to South Korea 22 years ago to spy for the North Korean government. But spying is not his job anymore, or at least, it’s not what he does in daily life. Now, Kim makes a living by selling fake Viagra pills smuggled from China and returns home every night to his wife and two loving children.