It's a very slow film but rather exciting. There are some slightly unbelievable twists here and there - why doesn't he kill the messenger? There are some moments of unsteadiness but it seemed that Melville was entering new territory with this one. Compared to the conversation, this film has even less actual story, and the revelation is delayed practically to the last frame.
I am not quite sure that I like this kind of totally undercooled acting but it definitively worked with this film. There are many details hinting at the complexity of the main character but nevertheless Delon mostly refrains from actually letting that show on his face.