I smoked something once that I believe must have had something else in it, PCP maybe. It was the late seventies, when hitchhiking was only extremely stupid, and my girlfriend and I were hitchhiking from Evergreen State College, to Spokane, Washington, where my mom lived. We ended up getting dropped off in the middle of Snoqualmie Pass in the middle of the night, so we were desperate. These two skier guys in a pickup truck seemed cool, even though there was only room for me to sit on my friend's lap- but Spokane was hundreds of miles away, so we climbed in. They offered us a joint and of course we smoked it, but then I had what can only be described as a really bad trip- I kept going in an out of hallucinations of death and car crashes, demanding that they stop the car, and then we'd be on the side of the road in the dark and cold and I would "come to" and not know why we were there- I'd say "Let's go, I'm freezing! Why are we standing here"
This went on for hours. Finally we got to Spokane and I freaked out in a Dennys. The we got to my mom's house, I took a sleeping pill and slept for 10 hours. When I woke up it felt that weird tripping the day before feeling-
yuck. That's the only time weed was not fun, so I am sure there was some crap in it.

NEVER hitchhike!
NEVER take drugs from total strangers!
I only survived those experiences so that I could warn you - it was bad, but it could have been MUCH worse.