Runaway, Runaway (1971)

 Runaway, Runaway (1971)

William Smith plays a detective who is looking for a runaway teenage girl who is trying to "find herself" in a Southern California commune. He plays kind of parental/authority figure to the girl (which doesn't stop him from sleeping with her, of course, this being the early 70's and all). There is a lot of groovy music, an extended acid freak-out scene, and the general lack of a coherent plot that tended to characterize these kind of films.

(IMDB  lazarillo)