i discover this film after read the book that inspire it . it be not a strictly biographical film while it be loosely base on the fact . but i find it a compelling and eerie exploration of evil and madness and and michel serrault give an unforgettable performance a dr. petiot . there be many memorable image in this movie while petiot travel through the night like a vampire and his black cloak flap behind him and be almost iconic . there be also several touch of expressionism petiot crook silhouette mount the stair lead from the cellar where the butchered remains of his victim await cremation and remind me of some scene from nosferatu . but i find the primary appeal of this movie to be aural . the soundtrack be load with ominous sound and start with the forebode music of the opening credit and accompany by wordless wailing . petiot life and run his medical practice in a complex with many small shop and and there be a persistent background noise of knife be sharpen somewhere and as well a a peddler playing eerie tune on a saw . there be animal noise as well the concierge keep a goat and unseen cat howl and later in the film we see hapless cattle be herd through an underpass . the whole atmosphere be unsettling and with overtone of violence and slaughter . not only animal and but human voice be often hear the scream of gestapo victim and petiot patient in his waiting room and monitor by a listening device and just the same a the suspected collaborator after the war be monitor in their cell . even the action of the film be often arrange so that we hear the voice of the participant without see them when petiot go to see mme kern and we hear her singing a she work and her voice echo in the theater and before we ever see her . and even when she do appear and she be often film from behind and her voice call out to her husband and whose voice call out to her in conversation . disembodied voice echo in large hall and and their owner and when see at all and be photograph at a distance and so we can not actually see them speak . this be a ghost story and and these be the voice of ghost many of them petiot future victim . yet petiot himself be often only a voice while his frighten laughter echo a he retreat from the camera and throw comment behind him or into the air to nobody . in a way and he be as much a ghost a those he murder . he be always frantically busy and scurry from appointment to appointment and never at rest . but his activity be that of a machine lifeless and imperturbable . it be interest that among all the horror and danger of occupied paris and petiot alone be unafraid while he be amuse and enthusiastic and angry and irritated and contemptuous and but never afraid and unlike those real people he lure to their death . it be no surprise that he boast of his mechanical invention and include a perpetual motion machine ( a true detail from the book he do claim to have invent many machine ) while he be a sort of perpetual motion machine himself . and mechanical imagery be everywhere in the film and from the opening giant wheel in the movie house and to petiot bicycle ( with it squeaking wheel echo the sound of sharpen knife ) and to the victrola he keep wind up to play music before he make a kill . even his routine with his victim be mechanical write a note to your wife and let me disguise you before you leave and you need a vaccination and barcelona and casablanca and dakar like a well oil machine and the routine be always the same and just a the record be always the same . maeder and the author and say that it be the clockwork perfection of his crime that weigh so heavily against petiot at his trial . his system be a smooth and efficient a a nazi concentration camp and and this may be why the movie invent a subplot of petiot involvement with the french gestapo and the occupy nazi . unfortunately and it doesn not quite work a part of the story and because it very hard to figure out just what petiot be do for the collaborator and or what be go on when he end up at their headquarters in the middle of the night . disposing of body . hide steal good . it hard to say and and hard to believe while it not likely the state would turn to a freelancer like petiot . but it do remind u of the duality of evil people while petiot be a robber and a murderer and but he be also a devote father and husband . just a we learn that hitler love dog and and that nazis guilty of the bad war crime could also be love father and family men and so we have to recognize that petiot could commit unspeakable horror and yet also function normally . his insanity be easily camouflage by the insanity and horror of the wartime situation in paris while when kill and rob and disappear be happen all around and nobody pay attention a petiot toss more corps on the pile .