It's easy to tell that The Crimson Rivers is a movie adaptation of a novel (Red Blood Rivers by Jean-Christophe Grange). Novels have the ability to weave extremely complex plots with many characters and ideas, and bring them together at the end. Movies can do this, but do not have the luxury of hundreds of pages worth of plot and character development. Sometimes, adaptations remain faithful to the story, but take away the essence of what made the novel enjoyable. The first half of The Crimson Rivers is good, then everything falls apart at the end. The end fails mainly because it is just too preposterous for a film. If the movie was half an hour longer, so that director Mathieu Kassovitz (Assassins, La Haine) could make a little more sense of the lame ending that comes out of left field, and turns what was a brooding mystery into a dumb action movie.

Two investigations are at the heart of The Crimson Rivers. Pierre Niemans (Jean Reno, Just Visiting, Tripwire) goes to the small town of Guernon to investigate a grisly murder. Fanny Ferreira (Nadia Fares, A Monkey's Tale, L'Enfant de la Nuit) found the dead body in the fetal position, with no hands, eyes, and a number of deep cuts. Niemans is a famous cop with a reputation for getting the job done, and he immediately begins investigating the locals. The clues lead to an elite university that Fanny attends. Reno plays Niemans as a legendary badass, but it's hard seeing why everyone is so afraid of him. There is not enough context for his character to give him such a level of gravity.

In a nearby town, Lt. Max Kerkerian (Vincent Cassel, Shrek, The Messenger) is investigating a grave desecration. The more he investigates, the stranger the case gets. Somebody is trying to erase the existence of a girl who died in a car accident nearly twenty years ago. They broke into her school and stole her pictures and records. Kerkerian is the opposite of Niemans. This is like nothing he has ever encountered. He is relatively new, and has a lot to learn. They eventually run into each other, and soon realize that they are working on the same case. As soon as they team up, The Crimson Rivers begins losing much of the tension and suspense it needs in order to succeed.

Things move quickly, but Kassovitz does a great job with the visuals. The murder scenes are grisly, each one more horrifying than the next. Kerkerian and Niemans are genuinely baffled at the events surrounding them, not realizing the extent of the murders. Kassovitz moves locations from an old university, to icy caverns and small towns, giving the air of a grand scope of events. He does overdo the camera circling around the protagonists, and one scene with Cassel fighting skinheads to a video game like announcer is just strange. Kassovitz just loses his momentum about two-thirds of the way through the movie. Gunfights and car chases replace a moody, thoughtful (and very bloody) thriller. The Crimson Rivers starts good, but takes a very lazy approach to an ending.