After 31 years of marriage, Kay and Arnold sleep in separate rooms, and he has lost interest in being intimate with her despite her efforts.
Their lives in Omaha have become routine; their anniversary present to each other is a new cable TV package. He goes to work as an accountant and she tends to their home and his meals in addition to keeping a job in a clothing boutique. Their kids are grown and detached from them.
Kay has not abandoned hope in improving their marriage, and finds a self-help book by a Dr. Feld, a marriage therapist who maintains a practice in Maine. Soon Kay tells Arnold that she has paid for a one-week therapy vacation with Dr. Feld, and he insists he will not go.
Instead, Arnold takes the advice of a colleague and tries to make Kay feel better with a pair of cheap earrings and some flowers. She is unimpressed, and pushes him to go on the trip, pointing out that he no longer has physical interest in her, and she wants to try to get some passion back in their marriage.
The next morning, Kay leaves for the airport without Arnold, and after some reflection, Arnold relents and joins her on the trip. In the small coastal town of Great Hope Springs where Dr. Feld has his office, the couple check into a modest hotel and Arnold insists on sleeping on the pull-out bed in a separate room.
They start their therapy with Dr. Feld the next morning and Arnold remains clearly resistant, saying their relationship is "adequate" enough without help, whereas Kay wants a marriage again. Arnold recoils in embarrassment when Kay describes how he does not touch her, and she says they dont talk about anything. Dr. Feld describes how they will need to do some tough work before feeling better.
Arnold protests that Dr. Feld costs too much and goes on complaining that the whole trip is a waste of time and money.
In their next session, they recall how they met in college and got married; years later they took to sleeping in separate rooms when he had a back injury, and Kay got used to it. When Dr. Feld asks, Arnold can't remember the last time they had sex, but Kay remembers the exact date over 4 years earlier. Arnold is very awkward as Dr. Feld asks more sexual questions, and he refuses to take on his assignment that the two of them hold each other for some time that evening.
Kay leaves the session in anger and runs away, finding a local bar where she has a glass of wine and talks to the friendly barmaid about the lack of sex in her marriage. Arnold wanders off and finds a museum.
After Kay returns, Arnold awkwardly volunteers to do Dr. Felds assignment, and the two of them lay down together in bed without touching, which Arnold thinks is "probably enough." After a moment, they roll toward each other and tentatively embrace. The next morning, Kay is quite happy to wake up and find Arnold still sleeping next to her, with his arm around her.
They explain their sense of progress to Dr. Feld, who quickly pushes them to move into further discussion of their sex lives. Arnold suddenly thinks they've had enough, but Kay persists with describing how she only sometimes liked intercourse and had orgasms, and does not masturbate because it makes her sad. Her fantasy is that someday they will renew their vows on a beach, but she laughs at the suggestion of having sexual fantasies. Arnold says he likes the missionary style; he felt that oral sex was not an option; he does not have erectile dysfunction. He slowly admits he's had a fantasy of Kay giving him "oral... at work... under the desk... at tax time," and of a threesome with a female neighbor.
That night at the hotel they start their next exercise, which starts with Arnold lying in bed fully clothed and Kay touching him, but he responds with disinterest until Kay moves toward his crotch, which arouses him to the point that he suddenly wants to stop. Then he abruptly goes to bed alone in the other room. Later, Kay tries delicately masturbating, and soon brings herself to arousal.
In their session with Dr. Feld the next morning, Arnold and Kay say their exercise made them aroused, but Arnold admits he wanted to stop, insisting he was not afraid of anything. He gets so mad he leaves.
When Arnold returns to the hotel that evening, Kay tells him Dr. Feld has agreed to refund half their fee, and they should plan to leave. She still maintains that she has nothing to move forward to in their marriage, and she was still hoping they could change.
The next morning, the couple return to Dr. Feld's office and Arnold persists with his anger about being pushed to talk about his feelings. He tells Kay that she always gets what she wants; she tells Arnold that he has lost affection for her. They admit their sex is bland, without desire. Arnold maintains that he was faithful by never cheating on her. Dr. Feld asks them to describe their best sex, and Arnold remembers a time when Kay was pregnant and they did it on the kitchen floor, which Kay recalls with tearful joy. Arnold says he remembers just wanting her, but he hasn't felt that way in a long time. Kay mentions she has a potent fantasy of having a new kind of sex with Arnold. Dr. Feld thinks of a new assignment.
Kay and Arnold go to a movie theater showing a French farce, where she begins to stroke his leg and tries to start fellatio on him. He is initially thrilled but she has trouble seeing and walks out in frustration. Arnold follows after her and tries to reassure her, but she walks away.
In separate sessions with Dr. Feld, Kay and Arnold describe how uncomfortable they were with the blowjob attempt in the theater. Kay wonders if she'd be happier living alone; Arnold says he does not want to be alone. Dr. Feld gives Kay a "prescription" for a book on sex tips; he asks Arnold to consider if he could make Kay happier.
Arnold walks to a local fancy inn and patiently waits until he can get a dinner reservation. That evening they have a very nice dinner and reminisce about their younger days, such as when they starting saying "I love you" to each other. Arnold later reveals that he got them a romantic room at the same inn. Kay is impressed with the arrangements, which include champagne and strawberries, and Arnold puts on Al Green's ultimate hook-up song "Let's Stay Together" to set the sexy mood. They begin making love in front of the roaring fireplace, until Arnold abruptly stops while he is on top of her. Kay accuses him of no longer being attracted to her.
In their last session the next morning, Dr. Feld assures them they have made a lot of progress, and recommends that they continue seeing a couples' therapist back in Omaha. They are clearly not so confident.
Kay and Arnold return to their house and resume living separate lives without talking to each other.
One night over dinner, Arnold tries to assure Kay that they're better off without changing so much. Kay wonders if she can still live like they do.
Kay and Arnold reflect on their marriage in a montage set to the ultimate break-up song, "Why" by Annie Lennox.
Kay packs a bag, planning to leave Arnold for a while. Later in the night, Arnold comes to her room and embraces her, and they make love, missionary style, yet with passion.
The next morning on his way to work, Arnold stops before leaving and gives Kay a deeply lustful kiss in the kitchen. As Arnold leaves in the driveway, they notice the neighbor whom he admitted fantasizing about a threesome with. Kay invites her to visit, and Arnold smiles inquisitively; Kay says to him, "That's not gonna happen."
Over the closing credits, Dr. Feld officiates as Kay and Arnold renew their vows at the beach. They declare their deep love for each other, and vow to make changes that they each want. They then celebrate with their kids and grandkids, eating lobsters and dancing.