The novel begins with a time of transition and new beginnings – after the death of their father, the Dashwood sisters and their mother move from their home, Norland, to a whole new life far away in Devonshire.
The central conflict shows up here, in the dashing form of John Willoughby. Marianne immediately falls in love with him, and her impulsive passion directs the course of much of the action from here on out – since Marianne is the more active of the two sisters, Elinor's thoughts and her own deeds often follow as consequences of her sister's passionate, headlong progress through life.
Everything seems to unravel as the three gentlemen involved in the Dashwoods' lives all disappear to London. We're not sure what's going on with any of them, and neither are Elinor and Marianne. Everything is unsettled and rather nerve-wracking. To make matters worse, Elinor is suddenly ambushed by unwelcome news of Edward's secret engagement to newcomer Lucy Steele, which certainly complicates matters, to put it mildly. Meanwhile, Marianne is preoccupied by thoughts of nothing but Willoughby.
Once in London, the complications only grow more…complicated. The nervous tension of the sisters explodes when Willoughby shows up once more. His rejection of Marianne, and the subsequent news of his engagement to an heiress throw the whole family into disarray – Marianne sinks into a deep depression, and Elinor isn't sure how to cope.
Both Marianne and Elinor are hopeless – Willoughby gets married, and Edward's marriage seems like a sure thing. Marianne sympathizes with her sister, but still can't pull herself out of her slump. When they're at Cleveland, Marianne falls ill as a result of her long, melancholy walks in the rain – her life is in danger. Elinor is terrified and essentially alone.
On the night of Marianne's recovery from the brink of death, Willoughby shows up to set the record straight. His conversation with Elinor is the first in a string of revelations that reorganizes everything in everyone's relationships. We learn, satisfactorily, that Willoughby really loved Marianne after all. Shortly thereafter, once the family returns home to Barton Cottage, reunited and recovered, we learn that Edward and Lucy broke up, and that he's loved Elinor all along. All of our mysteries are solved.
Finally, the way is clear for Edward and Elinor – he even makes up with his family, so we don't have to worry as much about their practical situation. After months and months of confusion, secrets, and struggles, everything is out in the open, and everyone is happy. Marianne gets over Willoughby (we think), and finally learns to appreciate Colonel Brandon. We end with the hint that Margaret, the youngest Dashwood, is grown up enough to become the center of her own love story. Will this cycle of intrigue and romance start again? We can only guess that the answer is yes.