Larry Coe is a Los Angeles architect who is married with two kids. He has a very bright wife, Eve. She is ambitious for him, but he wants to do work more imaginative than the commercial buildings he's been designing. He meets with Roger Altar, an author, to discuss building a house that will be an "experiment" and something Coe wants to do more of, something original.
Maggie Gault is one of his neighbors whose son is friends with his. She tells Larry she has seen some of his previous houses and thinks that the more unconventional houses are the best. This encouragement is what he needs from his wife but hasn't been able to get.
Both Larry and Maggie grow dissatisfied in their marriages. Larry's wife is too hard-headed and practical and Maggie's husband isn't interested in having sex with her. So they have an affair that involves meeting in secret. They both know what they're doing is wrong, and they are devoted to their children.
Felix Anders is a neighbor who snoops around and finds out about their affair. His leering and insinuations make Larry realize the risks he's taking. He tells Maggie that they shouldn't see each other for a while. Felix, in the meantime, makes a play for Larry's wife. In a way, Felix is a personification of the tawdriness of Larry and Maggie's affair.
After her near-rape by Felix, Eve wises up and realizes that Larry has been unfaithful. She confronts him. They agree to stay together and move to Hawaii, where Larry has been offered a job to design a city.
Altar's house is finished but still empty. Maggie drives up to take a look at it. Larry shows up and they talk about how they can never be together. Larry wishes he and Maggie could live in the house and if they did, he would dig a moat around it and never leave it. Maggie says she loves him.
The contractor for the house shows up and thinks Maggie is Larry's wife. They both take a moment to savor the irony of his remark and Maggie drives away.
Who is too hard-headed and practical?
Larry's wife