context: Kirk Douglas plays Larry Coe, a Los Angeles architect who's married with two kids. He has a very bright wife, Eve. She's ambitious for him, but he wants to do work more imaginative than the commercial buildings he's designing. Maggie Gault (Kim Novak), one of his neighbors whose son is friends with his son, helps him get a commission to build a house for an eccentric writer named Roger Alter (Ernie Kovacs, for comic relief). Both Larry and Maggie are 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 (or maybe he can't). So they have an affair that involves lots of walking on the beach and having drinks in oceanside hideaways. They both know what they're doing is wrong, and they each love their spouses in their own way and they're devoted to their children.Felix Anders (Walter Matthau) is a dirty old man neighbor who snoops around and finds out about their affair. His leering and insinuations to Larry makes Larry realize the risks he's taking and he tells Maggie that they shouldn't see each other for a while. Felix, in the meantime, makes a play for Larry's wife Eve in an unbelievably creepy scene. 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 and they agree to stay together and move to Hawaii, where Larry has been offered a job to design a city.Roger Alter'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 tells Maggie that he wishes they could live in the house and if they did, he would dig a moat around it and never leave it. Maggie doesn't say anything. Maybe she's thinking it's just as well the affair ended after all. The contractor for the house shows up and thinks Maggie is Larry's wife (which is strange because Eve has been a regular visitor to the building site). They both take a moment to savor the irony of his remark and Maggie drives away. On the way out of the driveway, one of the construction workers leers at her. She's not immune to one night stands, so she's already being put to the test. She drives back into their banal suburban enclave while Larry stands out on the house's balcony savoring the view of Los Angeles and no doubt thinking deep thoughts.This is a long film that moves along at a leisurely pace that reflects the time when it was made. Larry is a successful architect, yet he still can take his kids to the school bus stop and have time to carry on his affair with Maggie without his wife suspecting (even though he works at home, she doesn't keep much of an eye on him). None of the women in the film work; they don't have to because their husbands have jobs that can support a family on one paycheck. America was a more economically secure country then. The film has nice expansive feel despite the constricted lives the characters lead.
question: With whom is Maggie having an affair?
answer: Felix Anders