The Reptile (1966)

When his brother Charles Spalding mysteriously dies, Harry Spalding and his wife Valerie decide to move to the inherited cottage in a small village in the country. They are coldly received by the locals, with the exception of the bartender and owner of a pub Tom Bailey, who welcome them. His weird neighbor Dr. Franklyn, who lives with his beautiful daughter Anna, tries to persuade them to sell the house and leave the place, but the couple decides to stay. Harry and Valerie find that the locals are being killed by some snake and they feel threatened. When Anna asks for help and they trespass Dr. Franklyn's house, they find the horrible truth hidden in the place.

IMDb: https://www.imdb.com/title/tt0060893