Karen Black stars in three unrelated tales of horror. In the first, a professor is date-raped and subsequently blackmailed by a creepy student... but is there something even more sinister going on? In the second, an uptight young woman claims that her free-spirited twin sister is some sort of Satan worshipper. In the third, a lonely shut-in is attacked by a fucked-up little voodoo-doll thing.
I am fond of the horror anthology format. A short story, tightly and economically told with a strong central idea (often with a twist ending) can often be a more effective piece of horror than a feature length film. Formulaic perhaps, but it hearkens back to the old "campfire story" kind of horror, that eschews all excess details in favor of the horror. Tales From the Crypt (movie or TV show), Vault of Horror, The Twilight Zone, Three... Extremes are all highly approved by me. I think one of the reasons the Masters of Horror TV series was such a mixed bag was that it didn't stick to formula. Instead of telling small, well-crafted stories, the hour-long format led to a lot of episodes that felt more like abridged feature-length films.
Trilogy of Terror is an acceptable anthology film, worth seeing the once. The first and third stories bring the goods, but the film is hampered by its second story, which is plodding, uneventful, and depends entirely on a twist ending that you will guess within the first 30 seconds. The overall structure, namely having Karen Black play the leads in all three stories with each story being named after her character, seems to lend itself to some sort of feminist perspective. Instead, the filmmakers don't really exploit that element, except arguably in the first story, which takes the commonplace victimization of women in horror films and turns it on its head.