Rosemary's Baby, showing now in New York, was originally made in 1968. It was an unusual horror film for the time, in that it used humour and a knowing satirical edge to depict Satanism in a Manhattan luxury apartment house.

It is still unusual, considering horror movies today use unremitting gore and special effects to evoke fear. Roman Polanski used little more than surrealist dream sequences to build a growing sense of dread.

Rosmary's Baby, re-released to coincide with Polanski's latest, The Pianist, will be seen by many viewers newly interested in the director's early work. Those viewers will not be disappointed.

Rosemary's Baby tells the story of Guy and Rosemary Woodhouse, who move into the Dakota building in the Upper West Side. Guy is a struggling actor, Rosemary a housewife. How they can afford the Dakota is a question the movie does not address.

Like Repulsion, an earlier Polanski exercise in isolation, Rosemary's Baby is a faithful study of a lone woman's descent into the hell of dementia. Are the neighbors Satanists? Is her husband a willing partner in the ritual rape of his wife? Is her unborn baby, 'Andy or Jenny,' slated for use in a blood-filled Satanic ritual? Is her baby dead or alive? Is her doctor one of them? Is Rosemary going mad?

Polanski is the modern master of isolation. In Repulsion, an uncooked rabbit carcass gathering flies and maggots becomes a symbol for Catherine Deneuve's sexual and spiritual life.

In Rosemary's Baby, Mia Farrow gobbles chicken livers with the same greedy self-disgust. When she catches sight of herself eating the gelatinous blood-coloured meat she vomits into the sink.

But Rosemary's lust for flesh is ongoing. We watch her cook a steak. She puts a filet mignon into a pan with a dab of butter, turns the steak over with a fork, puts it on a plate and begins to eat.

Farrow is fabulous, perfect as the innocent wife with a dawning idea of the danger she is in. Halfway through the movie, she appears with a very short haircut. It is almost inexplicable, until she utters the magic words: "It's Vidal Sassoon, supposed to be very in!"

Ah, we think, the early sixties, when the strangest things were in. Farrow was the original flower child of the 1960s, a follower of the Beatles and the Maharishi Mahesh Yogi. During the time of Rosemary's Baby, she was Mrs Frank Sinatra, of course. And though she had appeared on television's Peyton Place, and in several forgettable movies, it was Rosemary that made her a star, for good reason.

Early on in the movie, attempting to repair her relationship with her husband, Rosemary tells Guy (John Cassavettes) that they need to talk more.

"Let's make this a new beginning," she says, on discovering she is pregnant. "Okay? A new openness in talking to each other because we haven't been open."

Guy is more than merely self-absorbed. Unknown to her, he has sold his soul to the devil in a pact that will give him fame and wealth. Rosemary, in varying stages of denial, must tell herself all will be well until, armed with a knife, she walks in on her neighbors and her husband in the movie's climactic scene.

That scene is almost camp, satirical to the extent of parody. Farrow, clutching a bread knife, gazes with horror at her new baby. The knife falls to the floor. Minnie (Ruth Gordon), the neighbour, rushes to make sure the floor boards are not damaged.

Minnie and Roman Castevet (Sydney Blackmer) are amazing creations, as are most of the old folks in Polanski's unsettlingly funny movie. They are banal and evil at the same time, and all the more effective for it.

The nosy Minnie is everybody's neighbour from hell, quite literally. She turns out to be more sinister than anybody could have thought possible. Gordon's performance won an Oscar. All these years later, it still astonishes.

As does Polanski. At this early stage, he is not yet the master of The Pianist. He is still casual with his gifts and not sure what to do with them. But, for instance in the surrealist sequences which are shot through with a bizarre humour, you can see more than a hint of his brilliance at work.