On Golden Pond opens in May with Norman and Ethel Thayer returning to their lake house in Maine. Norman is content to sit and read a book, but Ethel is busily moving furniture back in place, dusting, and generally getting the house ready for their summer stay. Through their conversations, the audience learns that they have been married a long time, love each other very much, and have different dispositions. They will be celebrating Norman's eightieth birthday, and he makes frequent jokes about his own mortality. Ethel is not amused, not so much because it upsets her as because she refuses to allow her husband to act like a victim.

Act 1, Scene 2

It is now June, and as she putters around the house, Ethel tries to give Norman updates about their neighbors. While she is very interested in the lives of her casual friends, Norman does not care enough to remember most of their names. He is more interested in reading the local wants ads in search of an easy part-time job. This seems to be more of a fun exercise for him than an actual job search. Later, Charlie stops by with the mail. He is a local man in his forties who has known the Thayers for many years. He asks about the Thayers' daughter, Chelsea, who is only a few years younger than he is. Their conversation reveals that he still harbors feelings for Chelsea.

In the mail, Ethel receives a letter from Chelsea, letting Ethel know that she will be visiting them for Norman's birthday. She will bring her new boyfriend, a dentist named Bill Ray. Norman responds with his usual sarcasm, but the audience can tell that there is a rift between him and his daughter.

Norman is also having bouts of memory loss, a reality he struggles to accept. Ethel sends him to pick strawberries, but when he returns early with an empty basket, he confesses that he did not know where the road was. It was a road nearby, and they had been to it numerous times over the years. His fears about his mental decline are exposed, and Ethel responds with compassion and reassurance.

Act 1, Scene 3

It is now July, and Chelsea arrives for her father's birthday. She brings her boyfriend and his thirteen-year-old son, Billy Ray. The unexpected arrival of the teenager delights Ethel, but Norman is initially unimpressed. After Billy has a tour of the house, Bill enters with the luggage and meets Ethel and Norman. Not interested in making Bill feel welcome, Norman gives him a chilly reception.

Ethel, Chelsea, and Billy go for a quick canoe ride, and Billy asks Norman if it is acceptable for him to share a bed with Chelsea while they are there. Norman responds with sarcasm and makes the conversation even more difficult for Bill. When Bill asserts himself and tells Norman that he will not tolerate being treated that way, Norman warms up to him. He says he likes him and that it is okay for him to share a bed with Chelsea. Billy returns, excited about the canoe ride, and sends Bill down to be with Ethel and Chelsea, who reportedly are skinny-dipping.

Norman asks Billy questions about his interests, his posture, and his reading. He comes to like the spunky, outspoken boy and sends him to his room to read the first chapter of Swiss Family Robinson. Ethel returns, and Norman pretends to be surprised that she has clothes on. She tells him that Chelsea has asked her whether Billy can stay at the lake house for a month while she and Bill go to Europe. Ethel likes Bill and wants to give her daughter a chance at happiness, so she asks Norman to do this for Chelsea. Norman agrees with surprisingly little reluctance.

Act 2, Scene 1

It is August. Norman and Billy have become very close friends, and they are getting ready to go fishing, even though Ethel warns them that it looks as if it will rain. Billy invites her to come with them, but she declines the offer. As she looks over her knickknacks and sings and dances alone, Chelsea enters. Ethel is surprised to see her, thinking that she has returned early, but it actually is the day Billy is supposed to return home.

Alone with her mother, Chelsea begins to complain about her difficult childhood. She feels that she tried very hard to please Norman but could never be what he wanted her to be. She also feels that Ethel was not there to protect and defend her. Ethel has had enough and says so; she believes that Chelsea should stop complaining about the past and live her life as an adult now. Chelsea announces that she and Bill got married during their trip overseas, and Ethel is thrilled.

It is now raining, and Norman and Billy return from their fishing excursion. Billy is excited to see Chelsea, but Ethel sends him to take a warm shower before he can hear her news. Then Ethel leaves Chelsea and Norman alone, and Chelsea tells him that she wants them to have a normal father-daughter relationship. He is caught off-guard, but agrees that they can try. He asks whether that means she will visit more often, and when Chelsea says it does, he says that it will make Ethel happy. Norman goes to take a shower, and Charlie stops by to deliver the mail and see Chelsea. They reminisce with Ethel.

Act 2, Scene 2

Now that it is September, Ethel and Norman are preparing to go back home. They have repacked their things at the lake house and replaced the dust covers on all the furniture. The phone rings, and it is Chelsea. She talks to both of her parents, and they make tentative plans for another visit. Trying to carry a heavy box, Norman strains himself and feels as if he is having a heart attack. Ethel panics but finds his medicine; as she is trying to call a hospital, he begins to feel better. She tells him how scared she was to feel that she was actually losing him. Together, they go to bid farewell to Golden Pond.