Slopped together quite carelessly, TWO SISTERS misses the opportunity to explore an interesting relationship between the title characters. It emerges as filler, duly issued as one half of the desultory double bill on Something Weird's Vol. 39 of its Dragon Art Theatre series.
Though IMDb classifies it as a 1974 film based on someone submitting a 1974 L.A. release date, the film is definitely of 1971 vintage. Not only does a closeup of a New Hampshire license plate in the first scene display the 1971 date, but a theatre marquee playing Dennis Hopper's THE LAST MOVIE proves it was 1971, since that film was shelved by Universal after only brief 1971 play dates.
Odd premise has Debbie linked to her younger sister Mary almost telepathically, in a way usually associated with twins. When Debbie feels something, her sister (even in a remote location) feels the same emotion, which in this case of course has to do with sex, it being Porn Territory. Their mother Agnes explains that this is a one-way street; Debbie does not feel what Mary is feeling in the reverse direction.
Mom is aware of this problem when she sees Mary masturbating one night, clearly under the influence of sis Debbie getting laid simultaneously out on a heavy date.
Given this unusual and convoluted starting point, one would expect something different here, but alas, film quickly devolves into all-sex porn after dangling the plot gimmick in front of a story-starved audience. Something briefly ventured, but nothing gained.
Typically there is the usual underage-baiting going on -it's not a coincidence that so much porn revolves around teenagers, whether they're played by 30 year olds or not. Clearly the closet pederasts in the audience must be served. In this case, Debbie takes Mary with a couple of guys they pick up on the street to a toy store (owned by co-star Ric Lutze, out solo without Rene Bond this time), and gets sis deflowered after they all "play doctor", surrounded by cute little stuffed animals and toys. One toy is even inserted in a vagina for good measure.
Sloppiness extends to Debbie even introducing herself as "Cindy" to the guys out on the street, even though she's Debbie again in the following scene inside the store. When the girls aren't having sex, film concentrates on ma Agnes getting it on. Odd casting has Agnes played by an actress resembling Mary Beth Hurt but with a huge rack (!), and she gives the fans a thrill by indulging in anal sex, not all that common in '71 movies.
Film falls apart in an attempt at surrealism for the final reel, that comes completely out of left field. The two sisters are marching wearily across a desert, on "the ultimate trip for both of us". No, they don't encounter Keir Dullea, but rather a motley, hippie-styled group of a black guy, priest and topless girl. The print ends abruptly just as the resulting orgy gets underway.