In San Francisco, recently-divorced physician Archie Bollen (Scott) and newly-married socialite Petulia Danner (Christie) are both dissatisfied with their lives. The problem is that neither knows what it is he or she wants. Archie had a perfectly loving marriage until he chose to end it; why, not even he can say. Petulia creates around her a frenzy of activity to escape something in her life.
The two embark on an affair as a result of simply another one of those inexplicable impulses that mark Petulia's decisions. Their different personalities — Petulia's whimsical intensity and Archie's gentle passivity — gives both a fleeting understanding of what it is they lack. However, that very combination of impulse and lack of resistance leads them to mutually reject their chance at a meaningful relationship.
- The '60s: A common audience response is that Petulia doesn't feel like a film of the sixties as much as a film about or looking back at the sixties.
- Aluminum Christmas Trees: The hotel built around a parking garage and Archie's Mid-Century apartment seem like sets created for the film to make ironic commentaries on America's infatuation with Modernism in The '60s, but they're actual San Francisco locations that still exist today.
- Amicable Exes: Archie and Polo ostensibly come across this way, but their love/hate feelings for one another lead to moments of tension.
- Beauty Is Bad: Petulia's husband David, played by young, hunky Richard Chamberlain, is an abusive jerk.
- Call-Back: The shots of Archie and his kids running around The Presidio are very reminiscent of Richard Lester's breakthrough films A Hard Day's Night and Help!, not to mention two of the birds at the penguin show being named Ringo and George.
- Chekhov's Gun: Due to the film's non-linear structure, characters, objects and even lines of dialogue that don't seem particularly important (or are even confusing) at first have their significance revealed later on.
- Cloudcuckoolander: Petulia.Archie: I should explain about Petulia. She is a kook.
- Darker and Edgier: It can be thought of as a more downbeat San Francisco-based version of Breakfast at Tiffany's.
- Deadpan Snarker:
- ArchiePetulia: I'm going to marry you, Archie.Archie: It's the Pepsi Generation.
- Strangely enough, the members of The Grateful Dead who play extras in the scene where Petulia is taken to an ambulance also count.Bob Weir: Bye bye, mama.Jerry Garcia: Write if you get work!
- Did Not Get the Girl: Ultimately Petulia decides to go back to David.
- Dramedy: There are some funny moments in the film, but it has quite a few dark moments as well. The New York Times called it "a romantic tragedy with comic detailing".
- Eiffel Tower Effect: Set in San Francisco, so there are shots of cable cars, Alcatraz, Coit Tower and the Golden Gate Bridge (though the bridge is only seen in a couple close-ups).
- Manic Pixie Dream Girl: Petulia fits the basic definition, but her portrayal is more like a deconstruction of the trope, showing the less-than-pleasant circumstances that can lead to someone developing that personality.
- Nothing Is Scarier: An unusual, non-horror example. We wonder what's wrong with Archie. There must be a reason why he left his family. He can't have left for no reason at all...surely?
- Shipper on Deck: Archie's colleague Barney keeps trying to convince Archie to get back together with Polo, mainly because his own marriage is in jeopardy and he wants reassurance that things can work out.
- Stalker with a Crush: Petulia and Archie both act as this at various times.
- Upper-Class Twit: David, intersecting with Rich in Dollars, Poor in Sense and verging on Idle Rich or Rich Idiot With No Day Job. Officially he's a "naval architect", but it's obvious that he doesn't really have any skills in life outside of being rich and being handsome.
- Would Hit a Girl: David (though it's kept offscreen).