This is a very enjoyable tough guy stylish French crime film based on the Lemmy Caution novels. There were 11 of them written by British author Peter Cheyney from 1936 to 1953 (there is an Omnibus on Kindle of them all) - this one is based on the first book in the series of the same name - the French title of the film is Cet Homme est Dangereux. Of the books six were made into films by the French and then of course there is Alphaville by Godard which was not based on one of the books or much of anything else that makes sense.
Eddie Constantine starred as Lemmie in all of them. Later on films with the character of Lemmie with Constantine again in the role were made in 1983, 1984, 1986, 1989 and for the last time in another Godard film in 1991, Germany Year 90 Nine Zero. Constantine was a fascinating figure with his craggy crumpled face broken up like the moon with bad acne in the past - but that just added to to his tough guy image in the films he made.
Born in Los Angeles he went to Europe to study opera - yup opera - but when that didn't work out he went back to America, got married and then went to France where he had an affair with Edith Piaf after he showed her one of his songs that he had written. With Piaf pushing him publicly, Constantine became a French pop star and got into film in 1953 with his role as Lemmie Caution. He was basically to remain in Europe for the rest of his life performing in films and singing - though he was also to appear in some American films. He died in 1993.
I read this book and it is fairly enjoyable as it moves fast and has a lot of bravado - but the dialogue Cheyney writes feels like he took it from watching the Warner Brother's crime films of the 1930's with Cagney, Raft, Bogart and Edward G. Robinson - all exaggerated tough guy talk that would make Hammett and Chandler blush - it was Cheney's attempt at writing American pulp. But it worked and he sold a ton of books though apparently France really took to his Lemmie Caution character. I am not sure many people in America have a clue who he is now.
The film follows the book very closely - though thankfully they re-wrote the dialogue and moved the action from England to France - but it starts about half way into the book - which may have been the right thing to do and certainly no worse than a slap across the face - of which there is a lot in this film - be careful if you go to France - slapping faces seems as popular as drinking wine. The story has a faint resemblance to Hammett's Red Harvest (1927) in which a detective cleans up a town by setting the two gangs against one another - a theme that was later used by Kurosawa and Sergio Leone.
There are some no good hard boiled dames, gunplay, knockabouts, betrayals, whiskey, cool cars and of course the face of Constantine that dominates the film like a giant Chesire cat grinning at the world around him.