When the branch leader position is open for Tuen Mun, Chicken decides to run for it and is up against fellow Hung Hing member "Barbarian", who resorts to ruthless Tung Sing member "Thunder Tiger" (Roy Cheung) for help in his candidacy. The triad also has to deal with finding a new chairman to the Hung Hing Society, Chiang Tin Yeung (Alex Man), Chiang Tin Sang's older brother, who resides in Thailand. Young and Dangerous 4 also brings in new characters first appearing among the Hung Hing ranks, such as Ben Hon (Wan Yeung Ming), "Sister 13" (Sandra Ng) and "Prince".