This soulful classic romantic drama is set in 1945, during WWII in and around the fictional Milford railway station. A married woman, with children, Laura (Celia Johnson), meets a stranger, a doctor (Trevor Howard) named Alec in the station's waiting/tea room, who kindly removes a piece of grit from her eye then leaves to catch his train.
During her following shopping trips to Milford, Laura bumps into Alec and a friendship begins to develop. Soon the meetings become a fixed arrangement.
At home in her living-room sitting with Fred, her husband (Cyril Raymond), we learn her story through the device of her voice-over telling him (and the audience) in her imagination what happened.
As their relationship grows Alec and Laura find themselves drawn to each other and falling in love. They begin to regularly attend the cinema and visit the surrounding area during short spells of time together. Finally they exchange kisses at the railway station to confirm their feelings. Yet Laura is both uncomfortable and elated, excited by the attention of a loving man but guilty about being unfaithful to her perhaps passionless husband.
Laura continues the deception and embarks on a passionate platonic extramarital affair. After much hesitation she gives in to Alec's pleas and joins him at his friend Stephen's apartment, but Stephen (Valentine Dyall) returns unexpectedly to his flat and a guilt-ridden Laura runs away. Alec later catches up with her and they agree to end the relationship but gradually rather than at once.
Alec then breaks the news that he is soon to leave the country after receiving a job offer from his brother in South Africa - he asks that she meet him next week for a final rendezvous.
This takes place the following Thursday, a day in the country, and a romantic but sad visit to the station waiting room where, over tea, their final goodbye is interrupted when they are joined by an acquaintance of Laura's. Alec leaves the two women stealing only a touch to Laura's shoulder as he goes to catch his train.
This scene was played out to open the film as a teaser, but now we have learned of its significance. Laura is devastated and has an emotional meltdown when she returns home to her husband and goes back over the events in her mind. She does not share this information with Fred, but he seems to know what she has been through, and has great sympathy for her.
We are left with the feeling that they will continue their safe, comfortable, middle-class marriage with a better understanding and appreciation in the reality of what they have.