A Stranger Knocks at the door of a young widow living in isolation in a seaside cottage. It is raining and he says he is lost, and she lets him stay for the night. In the morning, each feels a reluctance to separate, she because she is lonely and he because he is being pursued by police.

In the days that follow, they lead an idyllic existence. She sheds her mourning for her husband who was tortured to death as a resistance worker in World War II, and falls in love with the stranger; and he returns her love with at least some genuineness.

But this unhandsome man is strange indeed. He squashes his cigarettes precisely in the face of a figure printed on the kitchen ashtray. When in a little romp on the lawn she knocks over a pile of wood he has corded, he bellows a curse. When she says she is going in town for groceries, he twists her arm. And when in prying into her desk drawers he finds a revolver, he caresses it with his huge hands and pockets it.

Although he will not tell her, he was a collaborator during the Nazi occupation of Denmark, a torturer of resistance workers, and as it turns out, he was the one who tortured her husband to death. Neither knows this until she tells him that her husband's tormentor had an ugly scar on his arm.

He keeps his arm covered from then on, but one night she sees it. She gives him a chance to admit his guilt and, hopefully, his remorse, but he confesses only at gunpoint, spitting out with some satisfaction that he shot her husband in the neck after the torture. As she crumples at this news, he flings a glass of wine in her eyes and tries to escape. She shoots him in the back.

A Stranger Knocks is acted intensely by Birgitte Federspiel and Preben Lerdorff Rye. The complete isolation of the two characters magnifies the tension of the developing revelation of their relationship. The film is flawed only by a few trite lines and some occasionally self-conscious camera work.

It is disturbing, then, to discover that this film was banned in New York for almost a year because the State Board of Regents declared it obscene in two places. It is possible to find only one scene over which there might be some controversy (unless the other was cut for the Boston showing), and that one is entirely necessary and not at all offensive. The woman is in state of sexual ectasy when she discovers the tell-tale scar on her lover's arm. There could not be a more dramatic, or terrible, moment for her to make this discovery. Moreover, the eroticism is tempered by the physical appearance of Actress Federspiel; she has appealing, lambent eyes, and she has a plain face and physical proportions that are not apt to excite. She arouses sympathy, not sensuality. If any cinema sex is meaningful, this is surely it.

Whey the Board of Regents banned A Stranger Knocks is especially puzzling since they at the same time allow the glandular fudge of Times Square sexfilms and explicit nudity, nymphomania, and autoeroticism in art films like The Silence. If there must be frankness of sex, it is the kind in A Stranger Knocks that should be encouraged.