A very artsy film, Therapy consists of a series of ten "sessions" between various women and their therapist, played off-screen by Jincey Lumpkin. The women are all dealing with issues related to their sexuality. As they talk, they get increasingly aroused, get naked, and start to masturbate, some of them to orgasm, others not.
Conceptually, the movie is fascinating. Lumpkin has said that the various performers represent different parts of herself. It's not unarousing, either, though the sex is so well integrated into the movie's exploration of lesbian sexuality that it is almost hard to call it porn. Watch it because it's a great film. Watch it for the sex, too.
The movie is available online from Juicy Pink Box, as individual scenes. Note that these are sometimes different from (and, if so, then usually longer than) the scenes on the DVD. More of the women reach orgasm in that version.