A mutilated nude body is found by a couple of joggers and a rascal, Kang, is chief suspect.
Most of the film covers his life story in flashback, and the events which supposedly backgrouded his motives.
Young Kang wagged school with friend Chi, and got offside with both his parents. With Dad, for wagging school, and with Mum for being instrumental in Dad catching her in bed with another. Both parents slap him while the fight. Mum leaves, and Dad sends Kang to boarding school.
Things improve a little when he reaches 16. He's reunited with Chi, just back from the US. He invites Chi to stay, and they walk in on an apparently ordinary scene in Kang's lodgings, an orgy where his four gang mates are playing blind man's buff in the buff with two girls ! Also, a previous scene shows the gang to have committed a gang bang and attack on an innocent couple.
Kang also meets a lovely and good girl, Kitty, and he woos her. One night, on her birthday, Kitty, Kang and Chi are drunk and going home, when two gwailos attack. Chi and Kitty both die, and Kang develops a hatred for gwailos.
But, really, it seems all of society is against him. Almost everyone slaps him. The only ones who don't have just been killed.
So, when the gang decide to attack/rape a gwailo couple, what might Kang do ?