Savage Weekend (1979)

Marie Pettis has recently divorced her politician husband named Greg, who had been involved in a scandal in New York City. To decompress, she leaves for a weekend trip in upstate New York with her new stockbroker boyfriend Robert, her sister Shirley, and their openly gay friend Nicky. They arrive to the country late in the evening, and stop in a small town.

Robert, Marie, and Shirley pick up groceries at a market, where Shirley finds a sinister face mask that she decides to buy as a joke. Meanwhile, Nicky goes to the bar across the street for a drink, and is harassed by two homophobic men whom he beats up. They arrive at the remote farmhouse Robert has recently purchased from Otis, a local man whose father has died, and whom Robert has hired to build a large schooner, a project which is being housed in a barn on the property. Jay Alsop, an engineer and friend of Robert's, arrives to oversee the boat's progress. A lumberman providing the wood for the boat, Mac Macauley, tells Marie of a local rumor involving a young woman who was assaulted by the unhinged Otis, and hints that he may have been responsible for a murder. Jay develops a sexual interest in Shirley, while meanwhile Marie finds herself attracted to Mac. The following day, Jay goes down to the barn to check on Otis's progress on the boat; there, he is strangled by a killer donning the mask Shirley bought the day before, his body hung from the rafters so as to appear as a suicide. That night, the rest of the group dresses up for a formal dinner at the house. After dinner, Marie and Robert go for a walk on the property. Meanwhile, Shirley puts on a tango record and performs a striptease for Nicky. The two dance together on the house's second floor, and jokingly apply makeup to each other's faces. Marie and Robert discover Jay's body in the barn, and rush back to the house. The killer attacks Nicky upstairs, stabbing him through the head with a large sewing needle. Shirley is chased into the basement, where the killer ties her to a table saw and attempts to kill her with it, but cannot get power to the tool. When they arrive at the house, Robert and Marie are confronted by the killer. Robert discovers Nicky's body upstairs, and is thrown to his death out of the second story window. The killer then returns to the ground floor, where he reveals himself to be Greg. He tells Marie that he plans on taking her out into the lake and committing a murder-suicide. The next morning, Mac arrives at the house, and finds it empty. As he goes to investigate the basement, he turns on a light switch which activates the table saw, inadvertently killing Shirley, who has been tied to the table all night. Mac flees the house, where he encounters Greg attempting to bring Marie to the lake to kill her. Greg and Mac begin fighting and tackle one another to the ground. Otis arrives upon the scene, and kills Greg with a chainsaw. The film ends with Otis riding his bicycle to the local graveyard where he visits his father's grave.