When Mr. Dashwood dies, his son inherits everything, and despite having made a deathbed promise to his dying father that he would look after his three half-sisters and his stepmother, the son lets his obnoxious wife convince him to turn them out with only a token income, so they find themselves suddenly reduced from wealth and comfort to bare survival.
Eldest daughter Elinor, a woman as intelligent, sensible, and emotionally reserved as her mother, is played very well by Emma Thompson, who also wrote the screenplay.
Before she and her sisters are actually evicted from their Sussex country estate, Elinor meets the brother of her half-brother’s aforementioned obnoxious wife. (Yes, these relationships do get a bit hard to follow. Then again, my car was once totaled by my ex-wife’s cousin's ex-husband’s ex-wife. Let’s see Jane Austen top that.)
OK, let me try again: This is all happening in southern Regency England, in the early 1800s. Elinor's father had a son with his first wife, and under the rules of primogeniture he's the one who inherits the father's home. After his first wife died the father had married again, and Elinor and her sisters are the children of Mr Dashwood and the second Mrs Dashwood. This makes the three younger offspring half-sisters to Mr Dashwood's son by his previous wife. That son is married to a rather obnoxious woman who persuades him not to make any provision for his stepmother or half-sisters regardless of having promised his dying father that he would do so. Said obnoxious wife has a brother herself, and it's that brother (a half-brother-in-law to Elinor?) that Elinor meets before being evicted along with her mother and two sisters from their previous home. I don't know if that makes things any clearer, but I tried.
Anyway, the man Elinor meets, the brother to the obnoxious wife of her half-brother, is Edward Ferrars (Hugh Grant), who turns out to be nothing at all like his obnoxious sister. If anything, his personality has a great deal in common with Elinor’s, and they quickly become friends, which annoys his obnoxious sister and makes her even more obnoxious.
As I mentioned, Elinor has two sisters. The older of them, Marianne, is not much younger than Elinor and equally good-hearted but less rational and much more naive and romantic, basically the McCoy to Elinor's Spock, though they get along rather better.
Margaret, the youngest Dashwood sister, is a little girl full of enthusiasm for maps, tree houses, travel, and adventure. (As I recall this was all invented for the movie; the original novel doesn't have as much to say about the youngest sister.) Margaret shares Elinor's good opinion of Edward Ferrars, getting him to teach her fencing and making plans for him to accompany her on her future adventures (possibly involving piracy on the high seas) as her assistant, with responsibility for such things as swabbing.
But Elinor's budding romantic feelings and Margaret's fencing lessons both end when Elinor, her mother, and her sisters have to relocate to a cottage in Devonshire generously provided them by a jovial, wealthy, and gossip-loving older couple who are somehow related to them, which isn’t surprising since pretty much everybody’s related to everybody one way or another.
There the middle sister Marianne (Kate Winslet) makes quite an impression on a neighbor, Col. Brandon (Alan Rickman), a well-to-do bachelor. Alas for him, the attraction isn't mutual. Marianne thinks him too old and stodgy, and whatever hopes Col. Brandon might have entertained are crushed when she has a storm-tossed encounter with a dashing and handsome young hero, John Willoughby. In despair Col. Brandon changes his name to Snape and takes up the study of the dark arts, though I might be thinking of another movie. But Mr Willoughby might not be everything he seems.
Hugh Laurie has a small but memorable supporting role as another wealthy country gentleman whose chief form of exercise is rolling his eyes when his wife says something.
Unsurprisingly, given that it’s based on a novel by Jane Austen (her first published one, I think), the film is full of delightful romance, drama, and comedy, with plenty of interesting, well-realized characters, made even better by Thompson's script. (It does commit a few minor historical errors, but they're unlikely to be noticed. At least I didn't notice them until they were pointed out.) Thompson is also immensely likable as the reserved Elinor, whose joys and sorrows we infer in spite of her Vulcan-like emotional reserve. The one time she breaks down and weeps openly, it’s all the more affecting for being so entirely out of character.
I enjoyed the film quite a lot, but I was sometimes confused (wait a minute, who is that character related to again?), so I watched it a second time and liked it even more. I’d love to see a series of adventure sequels featuring an older Margaret trying her hand at exploration, naval warfare, and the like.
[Update multiple times within 48 hours of the original post in an effort to improve clarity and at least once since, not that it necessarily helped.]