If you think the City of Lights is a dangerous place to visit nowadays, you should see how it is in the historical thriller The Emperor of Paris (L’Empereur de Paris), which is set in the early 19th century under the reign of Napoleon.

Not only is the city depicted as a cesspool of open sewers, rotting pig carcasses and vicious robbers waiting to pounce upon their next victim, but it’s also a place where blood literally flows through the streets and bodies pile up faster than baguettes at the boulangerie.

Whether or not this is at all realistic is one of several problems with director Jean-Francois Richet’s violent and gory portrait of Eugene Francois Vidocq, the infamous criminal who transformed into an infamous criminalist, building the foundations of modern forensics and inspiring writers like Honore de Balzac and Edgar Allen Poe.

Vidocq — played with sweaty, gritty, wide-eyed physicality by Vincent Cassel — has already had his life depicted several times, including in a few silent movies, Douglas Sirk’s A Scandal in Paris (where he was played by George Sanders), a popular French TV series from the 1970s starring Claude Brasseur and a special effects-heavy production directed by Pitof (of Catwoman infamy) and starring Gerard Depardieu.

In this version, Richet — who directed the two-part Mesrine biopic (also starring Cassel) and the underrated Mel Gibson actioner Blood Father — winds up turning a potentially fascinating tale of crime, science, politics and power into a bloated and bloody mess (pun intended), with plenty of bone-crunching, gut-slicing carnage but very little, if any, substance. Along with screenwriter Eric Besnard (Babylon A.D.), he’s decided to eschew much of what makes Vidocq interesting in retrospect, such as how he conducted some of the first-known crime scene investigations and experimented with ballistics, anthropometrics and shoe prints, turning him instead into the swaggering hero of a brainless post-French Revolution shoot-’em-up.

Where Richet does excel is in delivering a handful of intense set pieces, including an action-packed opening that takes place on a hellish prison ship and several well-realized fight sequences set in the lower depths of Paris. He knows how to make violence look gruesome and painful, with Manu Dacosse’s camera covering all the gun, knife and sword duels from the best vantage points. Yet by the time The Emperor of Paris pushes through its ultimate Taxi Driver-style bloodbath, you’re left with a whole lot of corpses but a film that seems infinitely less intelligent than Vidocq must have been in real life, which is a pity given the rich subject matter available.

The prologue takes place in 1805, a year after Napoleon crowned himself Emperor of the French following a string of victorious battles abroad. We catch up with Vidocq, who’s already made a name as a criminal and career prison breaker, although now he’s stuck inside a floating jail filled with certified killers, MMA-style death bouts and a ghoulish ringleader called Maillard (Denis Lavant, in full snarling Denis Lavant mode). But the crafty Vidocq won’t remain aboard for long, teaming up with a fellow inmate, Nathanael (August Diehl), to make a break for it underwater.

Cut to several years later, where we find Vidocq selling rags in Paris under a false identity. He crosses paths with a beautiful pickpocket and prostitute named Annette (Scottish actress Freya Mavor), which causes him a heap of trouble. Yet you get the feeling that Vidocq likes trouble, or at least that it likes him, as he soon finds himself caught in a convoluted crime story that will bring Maillard and Nathanael back into his life, with deadly results.

By the time this has happened, Vidocq has already converted from thug to thuggish city detective, helping local police chief Henry (Patrick Chesnais) arrest scores of criminals who were once on his side of the law. There’s a whole subplot involving Henry’s pursuit of a Legion d’Honneur and his alignment with a powerful baroness (Olga Kurylenko).

Since The Emperor of Paris takes place before Vidocq began his groundbreaking innovations in criminology, there’s not much else of interest if you don’t like watching men with poor hygiene slash one another’s throats or blow each other’s brains out. Otherwise, the filmmakers clumsily hinge much of the plot around Vidocq and Nathanael’s combustive relationship, with the latter accusing Vidocq of betraying their kind during a monologue that sounds like a 19th century version of a “snitches get stitches” warning.

As with most of his roles, Cassel throws himself full throttle into this one, and he’s fairly convincing when he’s busting skulls or busting caps into skulls, which he does quite a lot of here. It’s just too bad that Richet, for whatever reason, didn’t focus on what makes Vidocq such an intriguing figure, preferring to cast him as the centerpiece of a movie that wants to be a French version of Gangs of New York, but never provides that film’s abundant historical context or memorable band of rogues.