The true-life story of the Papin sisters, two servants convicted of brutally killing their employer and her daughter in Le Mans in 1933, is the subject of Jean-Pierre Denis’ beautifully crafted and cooly unsettling “Murderous Maids.” The case was obviously the inspiration behind Claude Chabrol’s excellent “La Ceremonie” (1995), but in that instance the writer-director merely used the skeleton of the affair for a typically class-conscious contemporary thriller emphasizing the socio-economic differences between the perpetrators and their victims. Commentators have often posited such motives behind the actual event, but Denis eschews that kind of explanation in favor of a purely psychological approach, which implies that the older sibling’s inner turmoil and obsession with her younger sister derived from a physically and emotionally abusive family background. In this emphasis on the unconscious “Maids” is reminiscent of Peter Jackson’s marvelous “Heavenly Creatures” (1994), also an account of an actual murder committed by two young women; but while it shares with that film a rigorous attention to period detail, it differs in its resolute avoidance of any kind of artistic flamboyance in depicting the fantasies behind the characters’ actions. In that respect it’s actually more like another French true-crime film, Christian de Chalonge’s estimable “Docteur Petiot” (1990), about a physician who murdered Jews who relied on him for aid in trying to flee the Nazi-occupied Paris of World War II. “Maids” is a similarly clear-eyed, dispassionate portrait of a monstrous but somehow pathetic human being, and it also refuses to get too explicit in its explanations.

“Maids” also resembles “Petiot” in depending for much of its power on a masterful lead performance. In De Chalonge’s film it was the title turn by veteran Michel Serrault, who invested the doctor with a combination of manic energy and dry precision that was utterly fascinating–and frightening. Here it’s the performance of newcomer Sylvie Testud, who conveys Christine Papin’s tortured inner life and bursts of violence with admirable economy and restraint. The rest of the cast is excellent, too–Julie-Marie Parmentier both sweetly uncomprehending yet manipulative as the younger sister Lea whom Christine adores, Isabelle Renauld suitably unlikable as their self-centered mother Clemence, and Dominique Labourier appropriately snooty as their employer. The picture also recreates the atmosphere of the crime expertly. Shot in Le Mans itself, it achieves a strong 1930s ambience, and Jean-Marc Fabre’s cinematography emphasizes dark greens, blues and browns to generate a mood of quiet desperation, along with a nagging suggestion of dread.

The central problem with “Murderous Maids” is that ultimately it leaves the Papins’ act as random and inexplicable as it’s always been. Having rejected the socio-economic rationales posited in the past by many left-wing commentators, Denis falls back on a psychological explanation that he hasn’t been able to dramatize with full success. We’re introduced elliptically to the sisters’ unhappy family background–an absent father, suggestions of abuse, vague hints of an unsavory relationship between Clemence and her two daughters–but in the final analysis these factors, as harmful as they might have been, don’t add up to the horror of the final, shocking episode. One element of the equation–the physical relationship between Christine and Lea– could, if more deeply explored, have provided what’s lacking; but as it is the picture remains a tad unsatisfying. Still, there’s so much that’s excellent in it that it’s well worth exploring.