The film is based on the "Eight Immortals Restaurant murders" that took place on 4 August 1985 in the Hei Sha Wan section of Areia Preta, Nossa Senhora de Fátima, Portuguese Macau.

[1][2] While the massacre involving a family of 10 did occur at the restaurant, the alleged cannibalism is sensationalism inferred from the incomplete discovery of the victims' corpse, only finding limbs, and that there was a lack of telltale smell of decomposition despite the summer tropical heat.

Chan Chi-Leung brutally beats a gambler named Keung nearly to death for refusing to lend him money before burning him alive.

He quickly flees the Hong Kong police by burning his identification documents and changing his name to Wong Chi Hang.

Police officers Bull, Robert, King Kong, and Bo arrive on the scene before being joined by their supervisor Inspector Lee.

When confronted about it, Wong stabs him in the eye with a restaurant's reception check spindle and beats him to death with a large soup spoon before dismembering his corpse and turning it into pork buns.

Wong is caught trying to dispose of evidence linking him to Cheng Lam by Robert and Bo and is detained by the team while trying to cross the border to China.

After confessing, Wong is sent back to prison where after one final confrontation with Lee and Bull, commits suicide by slashing his wrists.

In Hong Kong, due to its explicit and disturbing depictions of sex, violence and gore involving the Wong Chi-hang character, The Untold Story was awarded a Category III rating (Persons Aged 18 and Above Only), the equivalent of the United States' NC-17 or X-ratings.

Despite its restrictive Category III rating, the managed to grossed an exceptional HK$15,763,018 at the Hong Kong box office during its theatrical run from 13 May to 2 June 1993.