In Pasadena, California, as Holly Davis attends an aerobics class, an earthquake interrupts the session. On the television at the Davis home, KKAC news reporter Sandy Dunlap is about to interview Holly’s seismologist husband, Dr. Thomas “Chip” Davis. As the interview starts, Holly receives a telephone call from Helga, the aerobics studio owner, asking her to fill in as class teacher for the evening after one of her instructors quit. Holly misses the interview but phones Chip to discuss accepting the teaching assignment. He encourages her to teach the class. At the aerobics class, Sandy Dunlap is one of the few students to keep up with Holly. In the locker room, Sandy mentions that Helga is struggling to maintain the gym, then asks Holly to join her for dinner. After some hesitation, Holly accepts. Meanwhile, Helga asks Holly to teach class on a regular basis, but cannot pay Holly until the following week. As Holly and Sandy have dinner at a nearby ice cream parlor. Sandy says she is divorced and was too ambitious to stay married. Holly maintains that it is an outmoded idea to think that you have to choose. Holly had a career as a dancer in television commercials but after she became pregnant with her first child, she quit, and does not regret her decision. Sandy admits she is ready to have a child whether she has a partner or not, and has been saving money. She has a lover who is handsome and smart, but it is complicated. Holly invites Sandy to dinner at her home the following Saturday. Back at the Davis home, Chip sees Holly in her leotard and is aroused, while she jokes that only earthquakes arouse him. As they make love, Holly wonders what it would be like to have another child because now that her children are older, she has less to do. On Saturday, Sandy arrives early to the Davis home and brings Holly a pair of glitzy workout shoes as a housewarming gift. Holly explains that she has also invited Chip’s colleague, Harry Crandall, to join them. Soon, Holly’s teenage children, Kim and Jeff, remark to their mother that Sandy interviewed their father on television, and Sandy suddenly realizes that her lover is Holly’s husband. Chip Davis is flustered when he sees Sandy. When Harry arrives, Chip asks him to act as if everything is normal, while Holly is oblivious to the tension. In the kitchen, Chip accuses Holly of inviting Sandy without his knowledge, and resents her attempt to match up Sandy with Harry. The dinner is awkward. When an earthquake aftershock occurs, Chip insists he and Harry must go to the laboratory. However, Harry remarks that the aftershock is small, and Chip sits down. Later, Holly is bewildered when her dinner party ends early. Chip again warns her not to fix up her women friends with his work mates. Later, he apologizes, and says he will attend a nuclear rally the following week in Washington, D. C. Holly would like to join him, but she promised Helga she would teach classes. Still later, Chip and Sandy meet at a diner, and talk about the dinner party fiasco. Chip explains that he loves them both. With Holly, he is stuck in a comfortable rut. With Sandy, he can be with somebody who is bright, attractive and independent. Chip reveals he is not looking for another wife, and believes Sandy is not looking for a husband, but Sandy wants to end the affair. Chip asks her to wait until he returns from his trip, but she does not see the point now that she knows Holly. Soon, Harry confesses that he respects Holly and resents covering up Chip’s affair. Chip responds that if he ends his marriage, Harry has permission to pursue Holly. Later, Holly leaves a voice message wondering why Sandy has not been to aerobics class, and asks her to dinner. Chip calls Sandy from the rally, and wants to see her when he returns. She insists that he focus on his wonderful family, and again refuses to resume their affair. Later at the television station, Sandy learns that Chip has been killed in an accident during a taxicab ride. She breaks the bad news to Holly at the aerobics studio. Later, after the funeral, Harry comforts Holly, by saying that Chip’s family meant everything to him. Holly thanks Sandy for helping around the house as friends and family mill around. Sometime later, Sandy stops by the Davis house to invite Holly for a game of tennis, but finds her friend depressed and in bed. Holly confesses that Chip did everything, and she is afraid and has no motivation to look for a job. Sandy thinks Holly should consider teaching aerobics. When Holly walks out of her bedroom, Sandy touches one of Chip’s tweed jackets before Holly returns. Soon, Sandy suggests that Holly buy Helga’s aerobics studio. Sandy wants to loan Holly $8,000 to buy the business but Holly refuses the offer until Sandy agrees to loan her half the amount and become a silent partner. After receiving a call from Harry, Holly stops by Chip’s office to remove his possessions. She cries as she packs his family mementos, but finds photographs of Chip and Sandy taken at a photo booth. Holly confronts Sandy at the TV station. Sandy says the affair started before their friendship, and she intended to tell Holly the truth later. However, Holly angrily responds that an affair is not acceptable just because the wife is anonymous. She punches Sandy and says she will pay back the loan because she does not want any of Sandy’s guilt money. Sandy insists she was just being a friend, then announces she is pregnant. However, Holly breaks off the friendship, and asks her mother, Ruth Chadwick, for a loan to repay Sandy. When Holly explains why she needs the money, Ruth reveals that Holly’s father once had an affair. Holly visits Sandy at home, and hands her a check. However, when Holly wants to know details leading up to the pregnancy, Sandy ends the conversation. Later, Holly spends an afternoon with Harry and his young daughter, Heather. Harry confesses that he has always been attracted to her. She reveals that she has been aware of his feelings for some time, but when she and Chip discussed it, they knew somehow that Harry would never act on his feelings. Then, she asks Harry if Chip strayed to improve his sex life, but Harry is uncomfortable and unaware of his friend’s motives. Later, Sandy meets with Harry to find out if Chip ever said he loved her. She is relieved when Harry tells her yes, and goes on to confess her mixed emotions over her pregnancy. She wants to have natural childbirth, but needs a partner. Sandy surprises Holly at home before the holidays. As they talk, Sandy is offended that Holly repaid the loan with interest. Holly apologizes, and says she also changed her mind about Sandy’s circumstances. Now, she thinks Sandy should have the baby. Sandy criticizes Holly for treating her as a bank and not as a friend, then proclaims she does not need Holly’s approval to have the baby. Months later, Holly visits the maternity ward, and Sandy criticizes her for sneaking around to see the baby. Holly wants Sandy to explain Chip’s attraction to her. Sandy says she does not know, but Holly answers her own question. Holly says she was attracted to Sandy because of her humor, openness, and vitality. Holly sees herself as a boring housewife, and finds it ironic that she is more interesting now that Chip is gone. Sandy says that Chip made a mistake but Holly would have forgiven him because, for the most part, their marriage was special. Later, the friends reconcile. When Holly escorts Sandy from the hospital, she discovers that Harry assisted Sandy during natural childbirth but never mentioned it. Meanwhile, Harry films Sandy leaving the hospital with his video camera. When Holly asks Harry why he never mentioned the natural childbirth, he says Sandy asked him to remain silent. When Holly asks if he has any other secrets, he kisses her and walks away. She calls him back, and he kisses her again. On the drive home, Sandy cries and insists that she will be the worst mother ever. Holly reassures her and gives her a hug. Later, all three watch Harry’s videos of new mother Sandy with baby, Steven. Before long, the screen reveals old footage of Chip at a park with Harry and his daughter, Heather. Harry offers to stop the film, but Holly calmly watches, and notes business at the aerobics studio is going well. Sandy congratulates Holly, and says she is considering a job offer. Holly compliments her friend, and encourages her to continue working as she raises Steven.