Henry and Muriel Rush are the owners of a duplex in San Francisco, where they live with their two adult daughters: 21-year-old banker Jackie and 18-year-old college freshman Sara, in a cramped, awkward arrangement. Henry is a cartoonist of a comic strip called Cosmic Cow, while Muriel is a former musician currently working as a photographer. When Henry and Muriel's downstairs tenant, Myron Rafkin, suddenly dies, the family discovers Rafkin was living a secret life as a transvestite, and the many mysterious women Henry had been opening the door for all those years were actually Rafkin himself. Sara comes up with the idea for her and Jackie to convince their parents to let them to move into Rafkin's former apartment. Henry rejects the idea at first, but after Henry interviews a couple of prospective tenants he doesn't approve of, Muriel convinces him that having the girls move in may not be such a bad idea.

With Sara and Jackie living downstairs, Henry has become a snoop-aholic. Sara asks for permission to go to Lake Tahoe for the weekend, leaving behind birth control pills that Henry assumes is hers and Jackie lets her navy boyfriend spend the night, causing Henry to hit the roof.

Jackie, who works at a bank, tries to make a money delivery to a supermarket, but finds it closed. After calling her boss, she finds herself in charge of a bag with $100,000 in it. Meanwhile, Muriel and Henry are convinced that the ex-convict plumbers are going to rip them off, but soon Jackie's bag of money enters the fray.

Sara befriends Monroe Ficus, a recently dumped young man, who quickly follows her all over the place even following her home. Meanwhile, Henry and Muriel plan on celebrating their anniversary but just before heading out for the evening they get a phone call from Sara and Monroe with news that they have been arrested.

Jackie and Sara have split the cost of rent but when Sara is unable to pay her half, Henry tells her to go out and get a job. Sara easily gets a job as a waitress, but Henry is in no way thrilled with the skimpy costume that she has to wear. This leads to a blow up between Henry and Muriel leading her to move in with Jackie and Sara.

The furniture of the previous tenant, Rafkin, has become Jackie and Sara's but when his sister shows up to claim his belongings, they find themselves in an unfurnished apartment. When Henry refuses to pay for new furniture, the girls decide to move out and into an unsafe part of town.

When Sara gets a part-time job at Jackie's bank, things go smoothly. Jackie quickly warns her of the branch manager, Mr. Wolfe, and his "friendliness" toward the women tellers. However, Jackie quickly finds herself changing her mind about Sara, when Sara begins dating him and then suddenly gets a promotion.

Henry is worried about his job when the new mystery loving boss, Arthur Wainwright, takes over and begins a steady practice of age discrimination. However, things may swing his way, when Muriel invites Arthur over for dinner which quickly embroils him in a quest to find the man who had snatched Sara's purse.

Sara and Monroe are ecstatic when a movie director decides Jackie and Sara's apartment would be perfect to film a movie. However, Henry and Muriel are totally unsure of the situation. Things get out of hand when a lion, being used for the film, gets loose and takes up residence in Henry and Muriel's kitchen.

Monroe has been struggling with the fact he is still a virgin and seeks out a psychologist for help. The psychologist suggests that Monroe hire a sex surrogate to solve his problem, but unfortunate circumstances cause Monroe to mistake Mrs. Rafkin for the surrogate, and the surrogate to mistake Henry for Monroe.

Sylvia Walker, an old college friend and recently divorced friend of Muriel's arrives in town for a visit and decides to make the most of the rest of her life. Meanwhile, Henry becomes insecure about his age after glancing over the obituaries and thinks he may be on death's doorstep soon. However, things turn around for him, when Sylvia makes a play for him.

Rich Holland, a man who took Muriel on the road with a band when she was young arrives in town looking just as young as ever. Henry soon feels old and becomes insecure, however, Muriel also becomes insecure when Rich takes an interest in Jackie.

Henry is not happy with the fact that he has been called in for jury duty. However, things get pressed when Henry's boss, Mr. Wainwright, wanting to avoid any problems associated with a possible strike, orders Henry to cough up next week's comic strip. This forces Henry to stay up all night and leads to him falling asleep in court the next day.

A football player, Buck Krulik, is in town and a fan of Henry's Cosmic Cow comic strip, so he comes by for a visit and has Jackie, Sara and Muriel fawn all over him. After admiring some of her photography, Buck remember her when a nude centerfold photo shoot goes awry and he calls her in to take over. However, she may not be quite ready for a male nude spread despite, Henry forbidding her.

A woman arrives at Sara and Jackie's door accusing Sara of dating her husband. However, the woman has the wrong Rush daughter, Jackie is the one and doesn't see anything wrong with it since they are separated. Still, she begins to feel her relationship coming to an end and quick.

Out of pity, Henry reluctantly allows Monroe to crash on his couch for Easter week when Monroe's parents decide they don't want him to visit them in Miami. Henry soon regrets his generosity when he learns that Monroe has ruined his unpublished Cosmic Cow drawings, and in turn his own planned vacation.

Henry is fired by Mr. Wainwright when he refuses to publish an apology for his recent Cosmic Cow comic strips that poke fun at President Reagan. Rather than face the indignity of taking unemployment compensation, he makes the regrettable decision to pursue his passion for painting and lets Muriel accept an offer for a full time job she doesn't really want.

Sara arranges for a medium to conduct a séance to connect Mildred Rafkin with her deceased brother in an attempt to find a missing antique broach. However, an accusation leveled by Rafkin's "spirit" threatens to split up Henry and Muriel, when the voice of the Rushes' late tenant accuses Henry of marital infidelity.