Sisters (1973) on Netflix

Grace Collier is a columnist with the Staten Island Panorama. She generally works on fluff pieces, but on occasion is allowed to do hard hitting stories which she prefers. From her apartment window one morning, she sees what she is certain is the stabbing murder of a black man by a white woman in an apartment across the way, the black man, seeing her, who tried to scrawl the word "help" in his own blood on the window. Reporting what she saw to the police, Grace gets little help from them, with who she has a bad relationship if only because of previous stories she has written on police brutality and racism. When the police and Grace arrive at the apartment in question, they find no dead body, no blood, and no woman matching who Grace saw commit the murder. All they find is the tenant, Danielle Breton, a young French-Canadian model/actress, who is visited by her soon to be ex-husband, Emil Breton. However, what Grace saw truly did happen, the dead man being Phillip Woode, a man Danielle just met on her latest job on a game show and her sex partner for the evening, and the murderess being Danielle's twin sister, Dominique Blanchion, who is possessive of her sister. Emil helped Danielle cover up the murder. Grace, with the help of a private investigator named Joseph Larch, tries to find out what is going on, including where the dead body is, which Grace believes they could not have moved out of the apartment between the time she saw the murder and when she and the police initially arrived on the scene. If Grace and Larch find out the truth, they will learn of an unusual relationship between Danielle, Dominique and Emil, one with strong psychological overtones based on the scar Danielle has on her right hip. And even if Grace and/or Larch discover the truth, they may not survive what Emil in particular is willing to hide at any cost to protect Danielle.