It's the 1940s, and the notorious Axe Gang terrorizes Shanghai. Small-time criminals Sing and Bone hope to join, but they only manage to make lots of very dangerous enemies. Fortunately for them, kung fu masters and hidden strength can be found in unlikely places. Now they just have to take on the entire Axe Gang.

Chi Mo Sai (Yuen Wah) meets Wong (Roger Kwok) in Auntie Fei's (Yuen Qiu) cafe and learns that Wong has photographic memory. He decides to exploit this skill by teaching Wong how to play Mahjong, but Fei, Wong's boss, strongly objects to it. Despite Fei's objections, Wong learns Mahjong from compulsive gambler Chi Mo Sai. He impresses triad boss Tin Kau Ko (Wong Jing). Wong falls in love with Tin's mistress (Theresa Fu) and is beaten by Tin's men. Wong then becomes crazy. Luckily, Fei cured him using Mahjong. Fei wanted Wong to beat Tin in the "King of Mahjong" competition and be the King of Mahjong. The film ends with a climactic "King of Mahjong" Competition. It is the only film made in 2005 to boast of having a sequel made in 2005.

28 years ago, Liang gives birth to a boy named "Little Bean Jelly" in prison. When the kid turns one, the mother and son lose contact. Years later, Green Dragon Group's henchman "Ghost" is ambushed during a mission and becomes blind. When Liang is released from prison, she meets Ghost. One wants only to complete the assassination, while the other wants to make amends to rebuild their mother-son relationship. By an unexpected combination of circumstances, this mother and son help each other redeem themselves and return to the right path.