There can be some debate on what exactly constitutes "horror," and that's a fair argument to have. You've got your horror films, and then you've got your thrillers. Because you can have thrills in horror movies and horror in thrillers, I'd argue that there can be cross-overs between the two. That brings us to today's film....
Don't Look Now
Directed by Nicolas Roeg, and based on a story by Daphne du Maurier (often a Hitchcock favorite), Don't Look Now tells the story of a couple who are extremely vulnerable, because they have recently lost their daughter to an accidental drowning. John Baxter (Donald Sutherland) and his wife Sharon (Julie Christie) venture to Venice after their daughter's death, as John has been assigned there for a job. Then, things start to become creepy.
Laura is contacted by two sisters, one of whom is blind and claims to be psychic. She tells Laura that she is in contact with her dead daughter. This obviously freaks Laura out. John is skeptical of the sisters' claims, and also distracted, as he has a job to do in Venice. But, as Laura's state becomes more fragile, John decides to investigate. And then he keeps seeing a small person dressed in a red coat -- a red coat not unlike their daughter's -- running through the streets of Venice.
It is my contention that Don't Look Now is indeed a horror film. It features two necessary elements: horror and vulnerability. It is particularly horrific for parents to lose their children, and so the film establishes this element from the start. And the characters of John and Laura Baxter are, indeed, vulnerable. This is made clear from their situation, and through the explicit sex scene between the two earlier in the film. Because as an audience, we identify sex as a vulnerable act.
Don't Look Now utilizes several tropes common to horror movies: a moody, grey color palette, dark and foreboding streets, an unnerving figure in the mist, creepy old women and of course the psychic element. Kudos should be given to cinematographer Anthony Richmond, as well as to director Nicolas Roeg, for creating a definitively creepy atmosphere for the film. It all comes together for one memorably uneasy experience.