Beginning in 1985, teenagers Chan Ho Nam (Ekin Cheng), his best friends "Chicken" Chiu (Jordan Chan), Dai Tin-Yee (Michael Tse), Pou Pan (Jerry Lam) and older brother Chow Pan (Jason Chu) idolise the local "Hung Hing" Society and one of its leaders, "Uncle Bee" (Ng Chi Hung). When Ho Nam and his friends are beaten by Hung Hing's "Ugly Kwan" (Francis Ng) and his men following a misunderstanding, they decide to join the society, following Bee.
Ten years later, in 1995, Ho Nam and his buddies have established themselves as Bee's enforcers, performing their first successful hit on Kwan's associate "Ba Bai" (Joe Chen). At the same time, Brother Fai Hung has the stuttering Smartie (Gigi Lai) carjack Ho Nam's Toyota MR2 and demand payment, but unfortunately she gets caught by Ho Nam and his friends and is punished by eating dozens of Chinese barbecue pork buns.
Seeing Ho Nam is making a name for himself in the society, Kwan attempts to buy him out and have Ho Nam work for him instead of Bee, but the gangster refuses. When he finds Smartie about to be forced into an adult film produced by Kwan's studio, Ho Nam takes her aside, claiming she is his woman. The indebted Smartie follows him, even beginning to fall for him. One day, Bee is tasked with an assignment by Hung Hing chairman Chiang Tin Sung (Simon Yam) to head to Macau and perform another hit. Bee orders Ho Nam and his men to execute the plan. Sadly, this was all a ploy on Kwan's doing: by using Chicken's fidelity to separate him from Ho Nam and falsifying information to chairman Chiang, Ho Nam and his remaining friends are ambushed by other triad members under Kwan. Chow Pan is brutally killed and Ho Nam is blamed for the failed hit. Friendships begin to tear apart when Chicken's girlfriend and Ho Nam are kidnapped and drugged by Kwan's men into sex, videotaping their actions as proof of violating secret society rules. With nearly all of Hung Hing looking for them, Chicken heads to Taiwan in exile.
1985年，陳浩南、山雞、大天二、包皮和巢皮一群在徙置區長大的朋友，在徙置區所屬的足球場內，碰到黑社會洪興社李乾坤（坤）強行索取保護費，引起雙方人馬衝突。此時，洪興社銅鑼灣的堂主鄧智勇（大佬B）阻止了坤。大佬B也接納陳浩南等人，並收為手下。
1995年，陳浩南一群人已投入大佬B旗下，出門辦事無往不利，成為最具有潛力的新生代人物。怎料，陳浩南的愛車Toyota MR2被長樂社的女賊蘇阿細（細細粒，臺譯「小結巴」）趁夜偷走，並向他勒索3萬港元，卻反遭眾人戲弄。某日，坤用20萬港元欲收買陳浩南，規勸他轉投他旗下，但被嚴詞拒絕。而且，陳浩南碰到細細粒被帶到坤經營的電影公司強迫拍攝色情電影，立即挺身用男友的名義，替她解圍，加上之前陈浩南等合力砍死靓坤结拜兄弟巴闭，此後坤對陳浩南的一言一行更加不滿。
洪興龍頭蔣天生吩咐陳浩南一群人到澳門處理賭場利益問題。但坤從中阻撓；坤趁山雞與應召女郎鬼混時，把他的女友可恩擄走；並且泄漏浩南等人行踪给敌方伏擊，致使巢皮命喪大橋。事后坤派傻強假裝解救身受重傷的陳浩南，並向陳浩南、可恩餵食春藥，使得兩人發生性行為。山雞與陳浩南亦因此反目成仇，之後山雞投奔臺灣三聯幫的表兄柯志華。
不久後，坤在會議上收買社團大老陳耀，罷黜龍頭蔣天生，自立為王；並拿出陳浩南與可恩性交的錄影帶，要求大佬B執行家法，大佬B被迫燃起大把線香，把陳浩南燙個體無完膚之後，踢出洪興社，浩南遠走西貢經營酒吧，不再過問江湖恩怨。但後來一直與坤針鋒相對的大佬B，遭到坤謀害，一家都被活埋。浩南大怒下欲重出江湖，為故主報仇，但無奈勢孤力弱，他的酒吧更被縱火，猶如喪家之犬。
走投無路的浩南，突然遇見了帶著一群臺灣兄弟的山雞，原來是前來幫助陳浩南的。山雞還帶來一筆巨款，指使其他洪興成員搗毀坤經營的處所，警方亦搜查坤的電影公司，從中發現有一批毒品後發出拘捕令，陳浩南一行人在坤母親壽宴時惡整其母，把坤引至暗巷，欲殺坤報仇，但坤奪槍並挾持包皮，卻被其早前羞辱過的巡警意外擊斃，陳浩南大仇得報，不但重回洪興社，並成為銅鑼灣的揸FIT人（堂主，臺譯「扛霸子」）
