This is a sometimes-cartoonish whodunit-style martial arts film.
Plot: A dying old man -- master of the Poison Clan -- wants his latest pupil (Yang) to track down five former students. To make sure they aren't misusing the training for evil, more or less. The problem is that the identities and faces of the five students are unknown. Yang is given one lead -- a retired (and wealthy) colleague, whose identity is also unknown. Unfortunately, that colleague is soon murdered for his money. The local police/judge try to find the killer(s) and it's a farce. The judge is corrupt, the courts are hilariously useless, and some of the police have been paid off. The body count keeps rising, and everyone is trying to figure out who's who.
The Five Venoms is ridiculous yet entertaining. Despite being from 1978, it's better than many modern Hollywood movies.