So much trouble with Leatherface could have been avoided. The hitchhiker ransacked the big house when he was alone and the huge key he had drove him wild with curiosity and greed. He then uses it to "unlock" the mystery door down in the basement.

If they never picked him up at that gas station, they could have had a nice party night afterwards in the house and Heather would have read that letter from her dear deceased Aunt that the lawyer gave her.

With Leatherface continuing to be locked downstairs, everyone could have lived happily ever after instead of being mince meat.