The movie is too clinical to be a commercial thriller and too expressive to be an objective case history. Ken Ogata plays Iwao Enokizu, whose almost random murder spree begins with the brutal stabbing of a truck driver. But the police investigation format drops away when Imamura suddenly jumps to scenes from the past. A wild, troublemaking son, Enokizu is pressured into one marriage so he'll 'calm down,' but instead brings home and marries a pregnant girlfriend, Kayo (Chocho Miyako). Flashbacks show the Enokizu family, part of Japan's Christian minority, being abused by a navy officer in WW2. Iwao's father (Rentaro Mikuni) is forced to sell his fishing boats and opens an inn. He rails against Iwao's irresponsibility, but eventually forms a relationship with Kayo when Iwao is in prison.

Life on the run requires Iwao to adopt disguises and think on his feet. He endears himself to the owners of another inn by cultivating an ingratiating personality and posing as a benign science professor. Haru Asano, the unhappy innkeeper's wife (Mayumi Ogawa) falls hopelessly in love with Iwao and refuses to turn him in, even when she finds out his true identity. Her aged mother Hisano (Niijiko Kiyokawa) forms an odd bond with Iwao as well, for she once served a long prison sentence for murder.

But grandma is definitely not in Iwao's league when it comes to killing. Enokizu stabs some victims and strangles others, all to get a little more money to keep going. We see him mercilessly swindle a woman trying to get a loved one out of jail, by posing as a lawyer who bribes judges. Iwao has barely taken her money when he links up with another lawyer on a train. He murders the man, stuffs his body in a closet and squats in his house while spending his money.

Vengeance Is Mine was adapted by Masaru Baba from a novel by Ryuzo Saki. Director Imamura uses Iwao Enokizu's murder spree to show a morally corrupted Japan, where twisted sexual situations seem to be the norm. Iwao's devout father gives into Kayo's sexual needs but refuses to marry her, as he is too old for her. When Haru's faithless husband has no girlfriend available, he rapes his wife. Hisano enjoys a vicarious sex life by peeping at other couples at the inn. The film's frequent sex scenes indicate a close relationship between sex and killing: Iwao seems content only when he's in control of other people.

The film gives no specific answer as to why Enokizu has become filled with so much hate for the world. The childhood memories of his father's persecution don't on their own provide a handy rationale. Iwao is alienated and contemptuous of everything he sees, especially his father's Christian teachings. Abusive and selfish young men like Iwao are mostly tolerated, while women seem trapped in confining roles. The inn where Iwao hides out regularly hires prostitutes to entertain the guests. One of them recognizes Enokizu when his pictures flash on the television, but balks at turning him in because of her shady profession. Iwao takes Haru to see a violent Russian war movie, and a public service announcement in the theater shows his face to the entire crowd. From then on it's only a matter of time before the cops track him down.

Vengeance Is Mine avoids the grandiose pseudo-psychology and mysticism that clog much of today's serial killer subgenre. In the clinical wrap-around story, Iwao's captors discover little about his motivation for killing. Iwao behaves as if he never really needed a reason to kill. Director Imamura aims at a wider social statement about Japan's changing values. The many scenes set in cluttered modern inns contrast with the calm, classical cinema of masters like Yasujiro Ozu, and in themselves seem a comment on the moral corruption of Japan.

Unfolding through multiple flashbacks, Ogata delivers a career-defining performance as a day-labourer and smalltime con-artist who, after killing two of his co-workers, embarks on a psychopathic spree of rape and murder. Eluding the police and public, Japan's infamous "King of Criminals" passes himself off as a Kyoto University professor, only to become entangled with an innkeeper and her perverted mother. Five years in the making, Vengeance is Mine transcends the limitations of run-of-the-mill criminal studies by presenting a portrait of a killer imbued with a poignant, tragic banality.

Shohei Imamura established his own independent production company, Imamura Productions, to allow himself more freedom away from the major studios, to choose riskier subject matter, and explore greater stylistic experimentation without compromise. He started his career in film as an assistant to Yasujiro Ozu before earning a reputation as a key member of the Japanese New Wave with Pigs and Battleships (1961) and The Insect Woman (1963). In 1975, Imamura founded the Yokohama Vocational School of Broadcast and Film which counts Takashi Miike (Audition, Ichi the Killer) among its many graduates.