Baby Sister is a 1983 television film directed by Steven Hilliard Stern. The film, which stars Phoebe Cates, Ted Wass and Pamela Bellwood, centers on a 19yearold girl who starts an affair with her older sisters boyfriend.
Annie once wanted to become a painter, just like her mother, but after her death she became isolated and gave up that dream. One night, David fails to save the life of his patient Billy, who has committed suicide. Annie witnesses his death and is reminded of her own mother. Both feeling very emotional, Annie and David end up kissing each other. The next day, Annie feels guilty, but David assures her it was only an innocent kiss. One night, Tom is throwing a family party. Annie gives him a selfmade painting, but the style reminds him too much of her mothers, which upsets him. They end up getting into a fight, after which Annie leaves. The next evening, Annie serves as a replacement for Marsha, who was supposed to attend a play with David, but wasnt able to make it. At first, they feel uncomfortable, but they end up sleeping with each other. Although they both feel guilty, they cant suppress their sexual attraction and start an affair. He plans on telling Marsha the truth, but Annie discourages him from doing so, afraid to hurt her sisters feelings. Unable to face her sister anymore, she decides to return to college after attending Marshas gallery opening.David tries to prevent Annie from leaving, telling her he is in love with her. They kiss each other in the clinic, until he is suddenly attacked by one of his drug addicted clients. He ends up getting severely injured and Annie brings him to the hospital. The truth about the affair comes out when Marsha visits the hospital and is told by a nurse Davids girlfriend helped him to the hospital. Upon confronting her, Annie admits to being in love with him. David takes all the blame on him and advices Marsha not to turn her back on Annie. In the end, just before leaving L.A., Annie is reconciled with both Marsha and her father, the latest assuring her she is not responsible for her mothers death. ........
Source: Wikipedia