WHOEVER THE serial rapist and killer was who terrorized Korea during the 1980s, he chose the right country and the right time.

Forensic crime solving was in its infancy. Samples in Korea had to be sent to the United States or Japan. Many of these submissions were sent back unexamined because the labs were overloaded with other requests. Detectives in Korea generally came out of a machismo, rough-and-ready tradition. Exacting confessions out of people, whether they were innocent or guilty, tended to be standard operating procedure. The careful gathering of facts and evidence was, at best, an abstract goal. They "discovered" suspects with their feet. And the 1980s was also a time when perpetual sirens required citizens to practice quick responses to air raids and biochemical attacks.

This fascinating social milieu puts original heft into "Memories of Murder," an involving and skillfully mounted film from Korean filmmaker Bong Joon-Ho that's based on a true story. In a small town near Seoul, the body of a young woman is found raped and killed. Two local detectives, Park Doo-Man (Song Kang-Ho) and Jo Young-Goo (Kim Nae-Ha), are assigned to the case. Doo-Man is a country boy who prides himself on an ability to see secrets in people's eyes. He likes to scrutinize his detainees up close, trying to psych them out with his powerful gaze. He is about gut conviction, facts be damned. His partner, Young-Goo, is an aggressive live wire who likes to beat suspects.

The first murder becomes part of a serial situation soon enough. Another woman is discovered dead with unspeakable injuries and violations to her body. In a country like Korea, where multiple killings are unusual, this proves overwhelming for the small-time detectives. But they are none too thrilled by the arrival of Seo Tae-Yoon (Kim Sang-Gyung), a smart aleck from the big city who is familiar with profiling, psychology, the quarantining of evidence and other sophisticated techniques of police work.

Predictably, the newcomer's subtle ways clash with the local partners, especially when he proves that all their suspects are innocent. Tae-Yoon also comes up with powerful clues of his own. It seems that the victims have all worn red when killed; the nights have always been rainy; and a certain song hit has always been requested on a postcard sent to a radio station just before the killer strikes.

Does any of this lead to the right man? How long does this case take? These are the mind-teasing questions that power "Memories," which is as exciting for its narrative twists and turns as for its Korean textures and rhythms. Writer-director Bong, who spent considerable time interviewing many of the real people involved with the case, fleshes the plot with rich human detail. All three detectives are distinctive and memorable, including Tae-Yoon, who insists that the chef not put sauce directly over his noodles at a restaurant. So are the suspects, including a mentally disabled man who complains that women grimace every time they see him and a pretty young man whose feminine manner might belie a brutal killer. Others stick in the memory, too, such as the kid who annoyingly echoes everything Doo-Man says when he's conducting his investigation of the first murder. And no matter how intense the search gets, the cops drop everything to watch a popular TV show of the time called "Inspector Chief." Finding the killer is one thing. But keeping up with a good show -- and normal life -- is quite another.

MEMORIES OF MURDER (Unrated, 132 minutes) -- Contains obscenity, nudity, masturbation and gruesome material involving rape and murder. In Korean with subtitles. At the American Film Institute's Silver Theatre.

Song Kang-Ho, center left, is a detective hunting a serial killer in "Memories of Murder."