Girl in the Box

Girl in the Box is a movie starring Addison Timlin, Zane Holtz, and Zelda Williams. In 1977, a girl is kidnapped and kept in a coffin-sized box. When her captors let her out, it's only to abuse her horribly. Will she ever escape?
A hitchhiking woman is abducted by a young couple and held captive for seven years, during which time she's tortured and forced to live as a slave to her captors.