During their excursion to Europe, Morris often visits with Aunt Lavinia in the Sloper household, and enjoys the luxuries of the Sloper's lifestyle, to pass the "unbearable" time. He enjoys parlor games, brandy, dinner meals, warm fires, and fancy cigars. Meanwhile in Europe in April, at a drafty and cold sidewalk table outside a Parisian cafe, Dr. Sloper remembers having visited with his wife - and possibly catches cold sitting there. He asks Catherine : "Have you given him up?" and learns that she still clings to her love for Morris - she has "not yielded one inch." He decides there is no reason to "prolong" the trip any longer, and they return to New York.

Upon his arrival, Dr. Sloper notices evidence that the usurper Morris has trespassed in the house - a half-filled glass of brandy and a cigar band-wrapper ("I can only think of one person...Is he upstairs in my bed?...So he's made my house his club").

He retorts to Catherine that she must be expecting to see Townsend soon, and threatens to disinherit her. He also angrily, cruelly and disdainfully insults her for her inferior nature and for her inability to "learn anything." He coldly claims that her sole attraction is her money, and that her only talent is her neat embroidery. He thoroughly humiliates her with his abusive words:

Dr. Sloper: Well, I suppose you'll be going off with him any time now.
Catherine: Yes, if he will have me.
Dr. Sloper: Why not? You'll be a most entertaining companion.
Catherine: I will try to be.
Dr. Sloper: And your gaiety and brilliance will make up the difference between the $10,000 a year you will have and the $30,000 he expects.
Catherine: He expects nothing. He does not love me for that.
Dr. Sloper: No? What else, then? Your grace? Your charm? Your quick tongue and subtle wit?
Catherine: He admires me.
Dr. Sloper: Catherine, I've tried for months not to be unkind, but now it's time for you to realize the truth. How many girls do you think he might have had in this town?
Catherine: He finds me pleasing.
Dr. Sloper: Oh yes, I'm sure he does. A hundred women are prettier, a thousand more clever, but you have one virtue that outshines them all.
Catherine: What, what is that?
Dr. Sloper: Your money!
Catherine: Father!
Dr. Sloper: You have nothing else.
Catherine: Oh, what a terrible thing to say to me.
Dr. Sloper: I don't expect you to believe that. I've known you all my life, and I've yet to see you learn anything. With one exception, my dear. You embroider neatly.

Already in the works is a plan (with Lavinia's help) to meet up with an awaiting and anxious Morris at 9:00 pm that evening. However, Lavinia is aware of the cross argument between Catherine and her threatening father, and instead advises Morris to meet (with Catherine) in the square during their shopping trip the following day. Catherine notices Morris outside in the rain and rushes to him. He asks two questions: "Have you been true to me, Catherine?", and "You've not changed your mind?" He then proposes a plan to elope and marry the following night:

• she will be picked up in a closed carriage at the corner of the square at 9:00 pm the next night
• they will be married in the country parsonage on Murray's Hill
• they will spend the night at an inn up the river
• the following day, they will go to Albany for their honeymoon

She implores him, because of their love, to not delay 24 hours. He is willing and promises to return with a carriage in two hours (at 12:30 am) in front of the house, where she will be "ready and waiting." When Morris suggests writing a letter to her father that "must melt his heart" and cause him to forgive them, she adamantly refuses, due to her father's despising attitude toward her. She reveals her father's threat of disinheritance (of denying her $20,000 a year):

My father doesn't like me...In this one thing, I know I am right...I understood it tonight for the first time in my life...We must never ask him for anything or depend upon him for anything. We must be very happy and expect nothing from him, ever.

Morris inquires: "Catherine, dear, he can't dislike you that much. He's bound to come around." She dashes his hopes for her father's money: "No, Morris. He will not, but even if he would, I would not." Morris is stunned: "I see."

Expectant, packed, and awaiting the carriage at the appointed time, Catherine is at the front window as Lavinia descends the stairs. After she describes their new romantic plan, Catherine feels no shame that her controlling father would be disgraced over her impulsive decision to leave without a chaperone and possibly spend the night unwed before being married. Lavinia is also shocked: "Catherine, are you quite yourself?" Catherine strongly asserts that she is completely rejecting her father (and disinheriting herself) by leaving one night early: "I will never see him again in my life...We dislike each other too much, Aunt." When she adds that she told Morris everything, Lavinia chides her naive niece for not being very clever: "Oh, you should have waited. Did...did he understand?" Lavinia acknowledges the reason why Catherine shouldn't have revealed so much to Morris - he is a fortune hunter who was expecting $30,000 a year - there were financial ramifications for rebelling against her father:

Morris would not want to be the cause of your losing your natural inheritance. He could not see you impoverished.

In the torturous scene, as time passes and no carriage arrives, Catherine becomes apprehensive that Morris, who may have second thoughts about a reduced natural inheritance, may not show up at her doorstep to take her away as promised: "He must come. He must take me away. He must love me. He must!...Morris will love me, for all those who didn't." As the night turns to daylight, Catherine weeps when the chimes ring in the early morning. She is totally crushed and heartbroken when he doesn't keep the rendezvous. She ascends the front hallway staircase to her third-floor room, lugging her heavy suitcase. She must know that she is again trapped in her father's house where constant criticisms from him have just been validated by Morris. The painful learning experience teaches her to never again be manipulated and deceived.

After returning from Europe, Dr. Sloper is confined to his bed and hasn't seen Catherine for a week. He is gravely ill with rales in his lungs, causing inflammation and possible congestive heart failure, requiring intensive nursing care. He announces: "I shall not recover," and requests that the maid prepare a liquid diet. And Catherine hasn't heard anything from Morris, who is in California according to Mrs. Montgomery. He borrowed the passage money from his cousin Arthur to move there.

She is callous, heartless, and cold to her Aunt and father, after being rejected and devastated so soundly. She informs her sick father that her departure is not "imminent" - "I am not leaving." He notices that she is flushed, her eyes look sick, and she's been weeping - and then he surmises: "You have broken your engagement." He knows the effort it took and the pain she suffered, but promises that her pain will pass in time. He tells her he is "most deeply proud" and admiring of her fortitude. She explains it wasn't her choice: "He deserted me," and then adds: "Don't be kind to me. It doesn't become you." She blames him for trying to protect her - speaking with a lashing "tongue" of bitterness toward her despising, logical and formidable father. Catherine defiantly insists that she would have married Morris even if he did want her only for her money. At the conclusion of their intense power struggle, her father retaliates by threatening to alter his will, and she fearlessly encourages him to disinherit her!

Catherine: You have cheated me. You thought that any handsome, clever man would be as bored with me as you were. It was not love that made you protect me. It was contempt.
Dr. Sloper: Morris Townsend did not love you, Catherine.
Catherine: I know that now, thanks to you.
Dr. Sloper: Better to know it now than 20 years hence.
Catherine: Why? I lived with you for 20 years before I found out you didn't love me. I don't know that Morris would have hurt me or starved me for affection more than you did. Since you couldn't love me, you should have let someone else try.
Dr. Sloper: You have found a tongue at last, Catherine. Is it only to say such terrible things to me?
Catherine: Yes, this is a field where you will not compare me to my mother.
Dr. Sloper: Should I have let him ruin your life? You'll find some honest, decent man someday. You have many fine qualities.
Catherine: And $30,000 a year.
Dr. Sloper: Yes, that should make it possible for you to choose with discretion.
Catherine: If I am to buy a man, I would prefer buying Morris.
Dr. Sloper: Don't say such things. You know him to be a scoundrel.
Catherine: I love him. Does that humiliate you?
Dr. Sloper: Catherine, promise me you are done with him.
Catherine: I won't promise.
Dr. Sloper: Then I must alter my will.
Catherine: You should. You should do it immediately.

She retrieves a piece of paper and pen, and begins writing out a revised will for her father, but he refuses to dictate the terms before considering the matter further, due to his illness: "I don't want to do it. I don't want to disinherit my only child." She only thinks he wants her to sit in the house - "rich, respected, and unloved" for the rest of her life. And then she aggravates him further by suggesting: "I may take your money and chase after Morris and squander it on him." She realizes that he will die before knowing what she will do. Shortly later, Catherine refuses to come to her father's bedside, even as he lays dying and requests her presence.

A number of years later, Catherine has matured into a more lovely, attractive, self-possessed, strong-willed woman and she has come into her inheritance. She is in charge of the Washington Square house, where she lives with her confidante Aunt Lavinia. She learns that Morris Townsend has been back in town for a week. According to Lavinia who accidentally ran into Morris, he asked many questions about Catherine, and seemed "very interested" that she hadn't married: "He fears that you never understood him, that you never judged him rightly." Lavinia tries to pressure Catherine to understand his side of the story (for her own happiness), although Catherine still believes she was deserted by the sweet-tongued charmer: "He has beguiled you again and you talk like a fool." Catherine refuses to even consider seeing him, but then the doorbell rings. Although she insists on refusing his entry and claiming she is not at home, she changes her mind after hearing his voice at the door.

Morris first asks: "Do I offend you by coming?" Catherine answers: "You should not have come." He wonders: "Can we be friends again?" He asserts that he never forgot her and struggled all the way from California to come back to her and explain himself. Thinking that he can excuse his own dastardly betrayal, he explains that he left in order to keep her from losing her inheritance, and begs for her understanding:

I've never ceased to think of you...Ever since the night I left, it's been the desire of my life that you should understand my motives...Catherine, it was because I loved you that I disappeared that night...But I knew that if I returned that night, I might have done you great harm. You know, my dear, no man who really loves a woman could ever permit her to give up a great inheritance just for him.

He further claims that he wasn't sure whether her father was testing him or not: "I had to make a choice. I chose your welfare rather than my own. Can you think of it that way?...Catherine, will you forgive me for the pain I caused you?" She responds reservedly: "I forgave you a long time ago." All the while during their dialogue, she leans back from him - repelled by his close embraces. Believing that he has been forgiven, the beguiling Morris boldly reminds her that they are free to love again, and that he needs her love - with a second marriage proposal:

We've only waited and now, now we're free. Nothing stands between us, Catherine...Let us make the rest of life happy for each other...By picking up where we left off. By marrying, Catherine...You would make me the proudest and happiest man in the world. And I will try and be a good husband to you. I'm older. I'm wiser now. And I know that you love me. I need that. I need it more than anything else.

She asks: "When would you like to marry me?" When he suggests in the "next month," she encourages him to be "impetuous" and propose to elope with her immediately that evening - as they had planned many years earlier. She asks for time to pack, while he makes arrangements and picks up his belongings at his sister's home, before meeting him at 9:00 pm. As he leaves, he promises: "You will have no regrets."

Although intrusive and effusive matchmaker Lavinia congratulates Catherine ("We have him back"), Catherine has no intention of marrying Morris. She draws the curtains in the front room, and insists on finishing her embroidery sampler work ("I must finish it now, for I shall never do another") - before revealing her plot to avenge and reject Morris so that he will never return and lie to her again:

Catherine: He came back with the same lies, the same silly phrases...He has grown greedier with the years. The first time, he only wanted my money. Now he wants my love, too. Well, he came to the wrong house, and he came twice. I shall see that he never comes a third time.
Lavinia: (surprised) Catherine, do you know what you're doing?
Catherine: Yes.
Lavinia: Poor Morris. Can you be so cruel?
Catherine: Yes, I can be very cruel. I have been taught by masters.

The climax of William Wyler's film is one of the most compelling and powerful ever made. On the night of a second promised elopement in a stunning climactic scene of ultimate revenge, Catherine calmly remains working on the embroidery until 9 o'clock when she hears a horse carriage approaching and a ringing doorbell - signaling her rendezvous with Morris. As she finishes the final stitches, she commands the maid to bolt the door from the inside ("Bolt it, Maria...Bolt the door, Maria"). Morris becomes more frantic and bangs on the locked door with the iron door-knocker, futilely calling out: "Catherine? Catherine." Catherine extinguishes the gas light in the front room, and listens at the door, but ignores Morris' entreaties.

Carrying another lighted gas lamp, the steely-eyed Catherine coldly walks up the long, extremely steep flight of stairs in the front hallway, filmed from in front of her. As Morris watches the light move away and diminish in strength, he becomes more frenzied as he beats vainly on the door: "Catherine, Catherine, Catherine!" She turns a curve at the top of the stairs, gaining perverse, proud satisfaction from jilting him (shown in a slight smile), and triumphantly fulfilling a promise to herself. In perspective, she has bested both her father (now deceased) and her only suitor - two males who condemned her to become a permanent spinster.

The film's 'The End' appears on the screen, before the film fades to the Paramount Pictures logo.