Savage Weekend

Savage Weekend is a 1979 American horror film directed by David Paulsen and starring Christopher Allport, David Gale, William Sanderson, and Caitlin OHeaney. The film follows a woman who retreats to upstate New York with her wealthy boyfriend, her sister, and friend, only to be stalked by a killer in a disfigured mask. Filmed in 1976 as The Killer Behind the Mask, the film was also titled The Upstate Murders before being released in 1979 by Cannon Films. It has been cited as an early prototype for the slasher film, predating Halloween and Friday the 13th.

Marie Pettis Marilyn Hamlin has recently divorced her politician husband, 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 Jim Doerr, her sister Shirley Caitlin OHeaney, and their openly gay friend Nicky Christopher Allport. 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 William Sanderson, 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 Roberts, arrives to oversee the boats progress. A lumberman providing the wood for the boat, Mac Macauley David Gale, 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. ........

Source: Wikipedia