This twisted cop mystery follows the efforts of the overworked Paris police to solve first, a murder in a couchette car, the dead body discovered only after all the other passengers left, and then the strange necking of many of the others before the cops can get to talk to them. There is great acting here from Signoret, Montand and others, and very amusing supporting parts (the seasoned crook and talker Bob will have you cracking up) but the film doesn't really hang together tight as a police mystery. I agree with an earlier reviewer that it spells trouble for you as a viewer that the passengers, whom we glimpse in half-darkness on the train, remain nameless for too long, and when they are identified by the police, the names are not steadily linked to faces.
It's confusing too that some of the characters suddenly muse into flashback kicking off from lines spoken to them on the train. This deepens them as characters but doesn't make the story concise. And at the police station, things are suddenly tossed in by phone calls in a way that looks haphazard. The root cause, I think, is that the film followed the book too closely, while Costa-Gavras knows how to create arresting, vivid scenes, he hasn't learnt at this point how to reimagine a storyline from writing so that it works on the screen, and so the movie seems a bit unfocused. When the final cause of the murders starts to crop up, it looks for too long like a joke element brought in for atmosphere.
It's not a bad movie at all; the photography is great, the final car chase is a winner (how often do you see a car chase in 1960s Paris?) and the acting is very good. Don't expect a murder story, though, with the tightness and relentless, upheld suspense of "Strangers On A Train" or even some episodes of "Columbo" or "Kojak".
