Newton Davis (Martin) is a struggling architect who tried to propose to his long-time love Becky (Dana Delany) with a fully-built house in their hometown, only for her to refuse. Unable to fully move on, Newton keeps the house and leaves it empty.
Months later, during a dinner party for his business, he befriends a waitress that had originally tried to avoid socializing with anyone by pretending to not know any English. After spending a night together, the waitress, Gwen (Hawn), decides to move into the abandoned house Newton had mentioned during their time together. Without money to buy furnishings or food, she convinces the town that she's Newton's new wife, and to put things on his tab. What originally starts as the perfect scheme quickly goes south when Newton decides to finally sell the house and learns of Gwen's antics...and then becomes complicated when Newton agrees to maintain the lie, because it's making Becky reconsider her feelings for him.
Tropes in this film:
- Bad Liar: Newton, whose on-the-spot additions to Gwen's lies end up nearly ruining their scheme.
- Becoming the Mask: As the deception of Gwen and Newton's marriage continues, Gwen actually begins to enjoy Newton's company. Eventually, the same applies to Newton's feelings for Gwen. By the end of it, Newton's decided that he likes Gwen's world of elaborate, exciting fiction better than the real thing, and is even building a house nearby for her fake parents to live in.
- Best Friend: Newton's butt-kissing coworker, who encourages Newton to take steps to move on from the past, and who refuses to show a project to their boss because he's worried about taking credit away from Newton.
- Betty and Veronica: Newton is supposed to be the bland, grounded, overly serious one in comparison to Gwen (the Veronica), so one can imagine how much of a boring milquetoast Becky (the Betty) is that she broke up with him for being too much of a dreamer.
- Brick Joke: When Gwen and Becky first meet, she explains that Newton's allowing her to charge things to his account because he's such a nice guy; the kind that just instinctively knows if you've had a long day and comes home with Chinese food so you don't have to cook. Later, Gwen realizes she's legitimately falling in love when Newton actually does bring home Chinese food after she's had a rough day.
- Brutal Honesty: Newton is upset at how the business he works for has sacrificed the creativity that originally inspired him, and is willing to say so to his boss' face. The boss, of course, isn't amused.
- Call-Back: On the last scene, Gwen is wearing the Christmas-like sweater she shows Newton several scenes before.
- Chekhov's Gunman: When Gwen invites Newton to her apartment the night they first meet, two homeless people she's familiar with are scavenging nearby. Later, when Gwen needs to find two people to pretend to be her parents, she chooses them.
- Con Man: Gwen convinces an entire town to give her food and furnishings without any physical evidence that she's actually married to the man everything's being charged to.
- Consummate Liar: Gwen's defining character trait.
- The Drifter: Gwen constantly moves and makes no lasting connections, which is how she easily left her job and relocated to Newton's abandoned house.
- Honor Thy Parent: After Newton makes a good impression at the party by singing "Too-Ra-Loo-Ra-Loo-Ral" at his boss' request, the homeless woman who is impersonating Gwen's mother has her own request - that he sing "Roll Out the Barrel." Gwen reacts: "Put a lid on it, will you, Mom?" The fake dad takes advantage of the roles they are playing and rebukes Gwen: "Don't take that tone of voice with your mother. Show some respect."
- Job Title: Because it's a movie about a house being occupied.
- Maintain the Lie: The majority of the plot is continuing to convince the town that Gwen and Newton are married.
- Manic Pixie Dream Girl: Gwen's crazy antics end up vastly improving Newton's life.
- Meaningful Rename: Gwen intentionally obfuscates what her last name really is because of how unsatisfied she was with her drab old life. And her first name isn't even Gwen.
- Operation: Jealousy: Newton is willing to keep Gwen around because she makes Becky reconsider how she viewed him.
- Opposites Attract: The main couple is Newton, an honest, barely-getting-by architect that dreams of better things, and Gwen, a lying con artist that lives vicariously but has no hope that she'll find true happiness.
- Paid-for Family: Gwen uses a homeless couple she's familiar with to act as her parents at a reception.
- Parental Abandonment: Newton and his parents originally cut ties after the house proposal incident, with the father upset at how Newton had also kept the costly-to-construct building a secret from them as well. However, thanks to Gwen's schemes, they end up fixing their relationship.
- Professional Butt-Kisser: Newton's Best Friend at his job admits that he's one, to the point that he'd surgically attach his lips if it meant keeping a job.
- Wacky Marriage Proposal: The movie begins with Newton proposing to the love of his life, Becky, by presenting her with a house he'd built for them...but she refuses, unable to see herself living with a dreamer like him.