It starts off like one of those 1950's Doris Day movies. Young, idealistic Rosemary (Mia Farrow) and new hubby Guy (John Cassavetes) move into a Manhattan apartment building called the "Bramford". Throughout most of the film we, as viewers, see and hear what innocent Rosemary sees and hears. There's a veneer of normalcy at the Bramford that belies what's really going on, behind our backs. It's the script's POV, therefore, that makes this film so chilling.
At the Bramford, which has quite a colorful history, you can hear through the walls. And, as Rosemary and we viewers soon find out, strange people lurk in other parts of the building. The strangest of all are Roman and Minnie Castevet (Sidney Blackmer and Ruth Gordon), superficially cordial, but a bit too inquisitive. Roman is retired. His wife, Minnie, wears tons of makeup and pawnshop jewelry, and gushes with praise for herbal cures, especially something called tannis-root. And Minnie's friend Laura-Louise (Patsy Kelly) wears thick glasses that make her eyes seem to bulge, and she talks with a strangely deep voice.
"Rosemary's Baby" is one of the great thrillers of all time. Given the underlying subject matter, can you imagine how this film must have come across to viewers in 1968? The strength of the film is the script, which through its plot and dialogue implies and suggests. Not until near the end do we, like Rosemary, find out the presumed truth. Suspense increases toward the end as Rosemary ventures into the inner sanctum of the Bramford.
The film's acting is great, and reinforces the strong script. I particularly liked Ruth Gordon, with her delightfully eccentric behavior and mannerisms. Production design and especially costumes are lavish and colorful. Clothes and hairstyles, as you would expect, are very 1960ish. Visual effects are minimal, and are used to enhance the story, not be the story.
Given the film's POV, the story is rather subjective. Its interpretation is based on Rosemary's perceptions, images, and fears. One could explain that Rosemary suffers from delusions. Or, alternately, one could explain that what happens is real. It's all in the interpretation. Either way, it's a great movie. It holds up well, forty years later, a tribute to its writer and director, Roman Polanski.