The Texas Chain Saw Massacre

Sally Hardesty (Marilyn Burns) and her paraplegic brother, Franklin (Paul A. Partain), travel with three friends, Jerry (Allen Danziger), Kirk (William Vail), and Pam (Teri McMinn), to visit the grave of the Hardestys' grandfather to investigate reports of vandalism and grave robbing. Afterwards, they decide to visit the old Hardesty family homestead. Along the way, they pick up a hitchhiker (Edwin Neal) who talks about his family who worked at the old slaughterhouse. He borrows Franklin's pocket-knife and cuts himself, then takes a Polaroid picture of the others and demands money for it. When they refuse to pay, he burns the photo and slashes Franklin's arm with a straight razor. The group forces him out of the van and drive on. They stop at a gas station to refuel, but the proprietor (Jim Siedow) tells them the pumps are empty. Read more on Wikipedia.