A second body of a murdered girl has been found in a drainage ditch beside a field of reeds, signalling the start of South Korea's first serial killer investigation.
Song Kang-ho is as ever excellent as Detective Park Doo-man, whose investigative technique stretches from looking deep into the eyes of suspects to beating a confession out of them.
Posing an alternative to these methods is Detective Seo Tae-yoon from Seoul, who has voluntereed to help find the killer using a bit of deductive reasoning and actual legwork.
These two approaches to the investigation keep clashing and coming together in amusing and often rather clever ways, leaving viewers to ponder whether the bad cops will pick up some of the good habits of their big city colleague...or vice versa.
CSI this isn't. There's not a mobile phone to be seen and although DNA evidence does eventually come into play, the Koreans have to send off their sample to the US for examination, creating a critical delay.
The location/period detail is superb. We loved the scene where Detective Park consults with his nurse girlfriend, his left arm attached to a drip, itself fastened to a branch in the lonely tree on the banks of the lake beside which they sit. Mainstream movies need more of this understated humour.
Bong's Mother was released this week in the UK and I can't wait to see it.