This was a simple story about a young college kid hitching rides in California, the people that he encounters, and the situations there in. Bruce Dern has an appearance in this movie, and you'll never believe this, but guess what? He plays the psycho. Here's the liner notes:

"Caution: Thumb Tripping could be hazardous to your health. Meg Foster and Michael Burns, two teenagers decide to become thumb trippers and hitchhike around California to learn about life. But their first ride turns into a nightmare when Bruce Dern and his sidekick take them on a life threatening trip. Foster and Burns escape and, after many hair raising events, meet up with a young married couple who like to party and get wild! The foursome get down to some serious drinking and when they're all sufficiently soused, things definitely get out of hand. Nothing will ever be the same between any of them... In the tradition of 'Easy Rider', 'Thumb Tripping' takes you on a wild adventure. Packed with action, violence, and sex, this is one ride you can't refuse."