In this romantic comedy from director Frank Oz, Steve Martin plays Boston architect Newton Davis, an impulsive dreamer who builds a bucolic dream home for his girlfriend (Dana Delany) as a means of proposing to her -- only she turns him down.
Three months later, the depressed Davis meets a waitress who calls herself Gwen (Goldie Hawn), though pretending to be Hungarian proves to be only the first of her many deceptions.
Davis has a one-night stand with Gwen during which he tells her the sad story of the house, which remains unoccupied just outside the city in his hometown of Dobbs Mills, because he can't bear to sell it. Following what seems to be a familiar path for this con artist, Gwen locates the house, figuring she can take up residence without anyone noticing.
During a trip to the local grocery, she ends up telling the proprietor she's Davis' wife while trying to charge her purchases to his account.
When she offers the same story to a local furniture dealer (Donald Moffat), unaware he's Davis' father, it triggers a string of fabrications in which the shocked Davis unwittingly becomes a co-conspirator. Seeing an opportunity of his own, Davis allows Gwen to stay in the house and agrees to go along with her story in hopes of winning back his jealous ex.
Of course, this also necessitates outlandish lie upon outlandish lie, leaving the whole enterprise forever on the verge of collapse.