Invasion of the Body Snatchers (1978)
Director: Philip Kaufman
I have not yet seen the 1956 film of which this is a remake, but if it is as good as Kaufman's version, I know I will like it. The 1970s version blends science-fiction and horror together, offering little by way of exposition, leaving us almost as much in the dark as the characters. The opening sequence shows us organic matter leaving a distant planet, making its way to earth through solar winds, and using plants to grow their own flowers. We then meet Elizabeth, a worker at the Health Department, who begins to notice changes in her boyfriend Geoffrey, who just happened to sleep near a small bouquet of these inter-planetary flowers.
Invasion of the Body Snatchers falls into the "bad" aliens type of close encounter films, though the alien themselves are not agressively hostile; they are simply acting on evolutionary impulses. Being gelatinous goo, they are rather undeveloped in terms of intelligence, and that is what gives this film is horrifying aspect. Humans, with our intelligence developed over many millennia, are so quickly reduced to basic impulses of procreating and consuming by these creatures, losing all emotions including empathy. This being the 70s, the ending is suitably pessimisitic, arguing for the power of conformity over an individual's fighting spiriting. While not the happiest of films, this is clever science-fiction horror, with good dose of gore to leave you squeamish.
And you won't trust pretty pink flowers ever again!