While giving in to her growing love, Laura detests herself for the intense enjoyment their meetings stimulate:

Oh, we had such fun, Fred. I felt gay and happy and so released. That's what's so shameful about it all. That's what would hurt you so much if you knew, that I could feel so intensely as that, away from you with a stranger.

Alec: You know it's happened don't you?
Laura: Yes. Yes I do.
Alec: I've fallen in love with you.
Laura: Yes, I know.
Alec: Tell me honestly, please tell me honestly if what I believe is true.
Laura: What do you believe?
Alec: That it's the same with you. That you've fallen in love too.
Laura: Sounds so silly.
Alec: Why?
Laura: I know you so little.
Alec: It is true, though, isn't it?
Laura: Yes, it's true.
Alec: Laura...
Laura: No, please, we must be sensible. Please help me to be sensible. We mustn't behave like this. We must forget that we've said what we've said.
Alec: Not yet, not quite yet.
Laura: But we must - don't you see?
Alec: Listen. It's too late now to be sensible as all that. It's too late to forget what we've said. And anyway, whether we'd said it or not, it couldn't have mattered. We know. We've both of us known for a long time.
Laura: How can you say that? I've only known you for four weeks. We only talked for the first time last Thursday week.
Alec: Last Thursday week. Has it been a long time for you since then? Answer me truly.
Laura: Yes.
Alec: How often did you decide that you were never going to see me again?
Laura: Several times a day.
Alec: So did I...

They both struggle against their budding, radiating love, believing that it will not bring them the true happiness that they both seek. Out of a sense of duty to their families, to moral and social propriety, and to their own repressed upbringings, their troubled, agonized love causes them to guard their actions and to feel pained by the pressure building from the disruptions:

Alec: ...I love you. I love your wide eyes, the way you smile, your shyness, and the way you laugh at my jokes.
Laura (whimpers): Please don't.
Alec: I love you. I love you. You love me too. It's no use pretending it hasn't happened cause it has.
Laura: Yes it has. I don't want to pretend anything either to you or to anyone else. But from now on, I shall have to. That's what's wrong. Don't you see? That's what spoils everything. That's why we must stop, here and now, talking like this. We're neither of us free to love each other. There's too much in the way. There's still time, if we control ourselves and behave like sensible human beings. There's still time. (She is overcome with tears.)

In the dark, shadowy underground subway tunnel-passage of the train station, Laura succumbs to Alec's first kiss:

Laura: Oh Alec, not here, someone will see.
Alec: I love you so.

As they passionately kiss for the first time, two large, long shadows of approaching passengers darken the tunnel's wall behind them, a newspaper swirls in front of them, and the roar of the approaching train is heard. The forceful speed of the noisy train represents their passion rising and crashing through the silence.

Sitting in the study with her husband, Laura is jarred from her memories by her husband's voice. She is confused and polarized by an inner struggle:

Fred: You were miles away.
Laura: Was I? Yes, I suppose I was.
Fred: You mind if we turn that down a little [referring to Rachmaninoff on the radio]. It really is deafening.
Laura: Of course not.
Fred: Shan't be long over this darling and we'll go up to bed. You look a bit tired, you know.
Laura: Don't hurry. I'm perfectly happy.

How can I possibly say that? 'Don't hurry. I'm perfectly happy.' If only it were true. Not I suppose that anybody's ever perfectly happy really. But just to be ordinarily contented. To be at peace. It's such a little while ago really but it seems an eternity since that train went out of the station, taking him away into the darkness. I was happy then.

Following their first kiss, Laura subjectively remembers her return to the train platform and her ride home to the dull English countryside. She is flushed with love - not even remorseful or ashamed:

As I went back through the subway to my own platform, I was walking on air. And when I got into the train, I didn't even pretend to read. I didn't care whether other people were looking at me or not. I had to think. (She peers at her own reflection in the dark train window and smiles.) I should have been utterly wretched and ashamed, I know I should but I wasn't. I felt suddenly quite wildly happy, like a romantic schoolgirl, like a romantic fool. He'd said he loved me. And I'd said I loved him. And it was true. It was true. I imagined him holding me in his arms. I imagined being with him in all sorts of glamorous circumstances. It was one of those absurd fantasies just like one has when one is a girl, being wooed and married by the ideal of one's dreams...

Her imaginary, impossibly-escapist, romantically "absurd," "schoolgirl" fantasy visions are projected onto various glamorous and exotic locations. She fantasizes being with Alec in a variety of romantic situations - the images are superimposed on the darkened window of the countryside as her train rushes to the suburbs. When she arrives at her destination, "all the silly dreams disappeared":

• Dancing to a waltz at a ball, under shimmering chandeliers.
• Going to the opera in Paris.
• Drifting and being romanticized on a gondola on Venice's Grand Canal.
• Driving away together in a fancy convertible.
• Sailing on the deck of a luxury ocean liner.
• Standing on a windy tropical island in the moonlight under palm trees.

I stared out of that railway carriage window into the dark and watched the dim trees and the telegraph posts slipping by. And through them, I saw Alec and me. Alec and me, perhaps a little younger than we are now but just as much in love and with nothing in the way. I saw us in Paris, in a box at the opera. The orchestra was tuning up. Then we were in Venice, drifting along the Grand Canal in a gondola with the sound of mandolins coming to us over the water. I saw us traveling far away together, all the places I've always longed to go. I saw us leaning on the rail of a ship looking at the sea and stars, standing on a tropical beach in the moonlight with the palm trees sighing above us. Then the palm trees changed into those willows by the canal just before the level crossing. And all the silly dreams disappeared. And I got out at Ketchworth and gave up my ticket and walked home as usual, quite soberly and without dreams, without any wings at all.

Laura recalls the first time she concealed the truth of her relationship from Fred, as she sits at her dressing table combing her hair with her back to him. When she remembers lying to him, her reflection in the mirror only displays passing glimpses of the the lower part of Fred's body:

Do you remember? I don't suppose you do, but I do. You see, you didn't know that that was the first time in our life together that I ever lied to you. It started then. The shame of the whole thing. The guiltiness. The fear.

Fred: Good evening, Mrs. Jesson.
Laura: Hello dear.
Fred: Have a good day?
Laura: Yes lovely. (He kisses her.)
Fred: What did you do?
Laura: Well I shopped and had lunch and went to the pictures.
Fred: All by yourself?
Laura: Yes, no not exactly.
Fred: What do you mean 'not exactly'?
Laura: Well I went to the pictures by myself, but I had lunch with Mary Norton. She couldn't come to the pictures with me 'cause she had to go and see her in-laws. They live just outside Milford you know. So I walked with her to the bus and then came home on my own.
Fred: Haven't seen Mary Norton for ages. How's she looking?
Laura: Oh very well. A little fatter I thought.
Fred: Hurry up with all this beautifying. I want my dinner.
Laura: You go on down. I won't be five minutes.

Furtively, Laura phones Mary Norton (Marjorie Mars) to ask her a favor: "Will you be a saint and back me up in the most appalling domestic lie?...My life depends on it." That night in her bed, Laura is tormented about the long wait until the next Thursday - their sixth meeting together:

That week was misery. I went through it in a sort of trance. [To a sleeping Fred] How odd of you not to have noticed that you were living with a stranger in the house. Thursday came at last. I had arranged to meet Alec outside the hospital at 12:30.

Alec: Hello.
Laura: Hello.
Alec: I'd thought you wouldn't come. I've been thinking all the week that you wouldn't come.
Laura: I didn't mean to really, but here I am.

They go for lunch in a "grand" restaurant in the Royal Hotel, where Alec orders a bottle of champagne for the two of them. Laura remembers that he asserted they must have champagne because "we were only middle-aged once."

We were very gay during lunch and talked about quite ordinary things. Oh Fred, he really was charming. I know you would have liked him if only things had been different. As we were going out, he said that he had a surprise for me, and that if I would wait in the lounge for five minutes, he'd show me what it was. He went out and down the steps at a run, more like an excited schoolboy than a respectable doctor.

While waiting for Alec to return, out of the dining room approaches Mary Norton and her rich cousin Mrs. Rolandson (Nuna Davey), whom Laura suspects watched them all throughout their lunch. Mary recognizes her and comments on her dining partner. Mortified with embarrassment, Laura matter-of-factly explains that she had known the "charming and very attentive" (in the cousin's words) Dr. Alec Harvey for years. As Mary bids Laura (and Alec who has returned) goodbye, she tells her: "I do so envy you your champagne."

Alec's "surprise" sits by the curb outside - a "little two-seater car - Alec had borrowed it from Stephen Lynn for the afternoon." They go for a ride into the country in the borrowed convertible and stop by a little stone bridge and a stream, but Laura is disconsolately guilty:

We leaned on the parapet of the bridge and looked down into the water. I shivered and Alec put his arm around me.

Alec: Cold?
Laura: No, not really.
Alec: Happy?
Laura: No, not really.
Alec: I know exactly what you're going to say. That it isn't worth it. That the furtiveness and lying outweigh the happiness we might have together. Isn't that it?
Laura: Something like that.
Alec: I want to ask you something, just to reassure myself.
Laura: What is it?
Alec: It is true for you, isn't it? This overwhelming feeling we have for each other. It's as true for you as it is for me, isn't it?
Laura: Yes, it's true. (They kiss as the Rachmaninoff music swells.) We must have stayed on that bridge for a long time, because when we got back to Stephen Lynn's garage, it was getting dark. I remember feeling that I was on the edge of a precipice. I think Alec felt that too. You see, we both knew how desperately we loved each other.

Laura vehemently and guardedly refuses to accompany Alec into Stephen's unoccupied apartment to return his car keys, accurately reading his subtle invitation to be private with her ("I refused rather too vehemently. Alec reminded me that Stephen wasn't coming back till late but I still refused.") Shortly later as they walk along a dark street near the train station, Alec again requests her company to return to Stephen's borrowed apartment:

Alec: I'm going back. I'm gonna miss my train.
Laura: Back where?
Alec: To Stephen's flat.
Laura: Oh, Alec. (As an express train's whistle gets closer and whizzes by, sending up billowing clouds of steam, they embrace each other.) Alec, I must go home now. I really must go home.

Laura dashes off toward the refreshment room of the railway station and orders a cup of tea, while Alec walks away in the opposite direction to stay at his friend's flat. Comic relief is provided when two working class officers order alcohol, but the insulted hostess Mrs. Bagot refuses to serve them after hours:

Worker: Come off it, mother, be a pal!
Myrtle Bagot: I'll give you mother, you saucy upstart!

When the 5:43 train from Ketchworth is announced, an inner debate rages in Laura's mind from the previous conversation:

Laura: I really must go.
Alec: I'm going back to the flat.
Laura: I must go home. I really must go home.
Alec: I'm going back to the flat.
Laura: I'm going home.

Although she enters the train compartment, she abruptly leaves the car just as the train begins to pull away, and tells the other passengers: "Excuse me. I've forgotten something." She walks toward the apartment and joins Alec in his friend's flat at the start of a rainfall (the rain marks the beginning of the end for them). Overwhelmed with inescapable guilt over their clandestine affair, Laura's nerves are frayed by the thought of committing adultery in a tryst, so she non-chalantly begins talking about the rainy weather and the damp wood on the fire:

Laura: (looking in a mirror with her back to Alec) I'm an absolute fright...
Alec I hope the fire will perk up in a few minutes.
Laura: I expect the wood was damp.
Alec: Yes, I expect it was. Do sit down, darling.
Laura: I got right into the train and got out again. Wasn't it idiotic?
Alec: We're both very, very foolish. (They kiss again.)
Laura: Alec, I can't stay, you know. Really I can't.
Alec: Just a little while. Just a little while.

When they hear the sounds of Stephen Lynn (Valentine Dyall) returning unexpectedly due to a cold, Laura fears being discovered and leaves by the back kitchen door, as Alec greets his friend in the living room. Stephen notices Laura's scarf on a chair and immediately interprets Alec's intentions. [This is one of the few illogical instances in the film when a conversation takes place in Laura's memories/fantasies that she doesn't witness.]:

Stephen: You know, my dear Alec, you have hidden depths that I never even suspected.
Alec: Look here, Stephen...
Stephen: For heaven's sake, Alec, no explanations or apologies. I'm the one who should apologize for returning so inopportunely. It's quite obvious to me that you are interviewing a patient privately. Woman are frequently neurotic creatures and the hospital atmosphere is upsetting to them. By the rather undignified scuffling which I heard when I came into the hall, I gather that she beat a hasty retreat down the back stairs. I'm surprised at this farcical streak in your nature, Alec. Such carryings-on are quite unnecessary - after all, we've been friends for years and I am the most broad-minded of men.
Alec: I'm really very sorry, Stephen. I'm sure that the whole situation must seem inexpressably vulgar to you. Actually it isn't in the least. However, you're perfectly right. Explanations are unnecessary, particularly between old friends. I must go now.

After remaining gallant, Alec is asked to return Stephen's latch-key and he thinks his friend is "very angry." Stephen describes his own mood, however, as "just disappointed" rather than angry.