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In her second feature, I Do… Until I Don’t, deft writer-director Lake Bell explores the seven-year itch. As in her first film, In a World —a look at the challenges of female voiceover artists—Bell co-stars in this ensemble comedy, but she lets another brash, vile character say the things we all may be thinking about that ultimate love obliterator, monogamy. Of course, this is the most cynical view of exclusivity, however, and cockle-warming is all but guaranteed to slip into the script at some point.

The relationship-busting villain is Vivian (Dolly Wells), a bitchy Brit who descends on Vero Beach, Florida, to film a documentary that she hopes will prove her pitch that marriage should be a seven-year contract (with the option to renew). She recruits couples whose togetherness seems to have overstayed its welcome, such as Harvey (Paul Reiser) and Cybil (Mary Steenburgen), and later Alice (Bell) and Noah (Ed Helms). Whereas Cybil immediately starts negotiating when Vivian approaches her in a diner—a little too quickly and cleverly, as if she’s a veteran of the movie biz—Alice begs to be part of the project and signs on for zero compensation. Vivian isn’t interested in Alice and Noah because their issues seem too minor. But Alice worships Vivian, so she’s willing to stage-sink her marriage on camera.

Why sweet, timid Alice is a fan isn’t really explained. Bell shows her character only at a talk Vivian gives to a roomful of sad-looking women, telling them, “Don’t be daft. Love is not sustainable, nor is marriage.” Alice seems too easily put off by the ickiness of the world in general to follow such a sharp-angled shrew. But it’s a quibble in an overall witty script.

Alice’s real problem comes when Noah finds out—erroneously—that they’re not only participating in the documentary but getting paid a sizable amount of cash. This discovery occurs when Alice’s hippie sister, Fanny (Amber Heard), and her husband, Zander (Wyatt Cenac), visit and mention that they’re doing the project. Though it’s not because their relationship is bad—it’s because their relationship is open, an arrangement that Vivian apparently thinks of favorably.

Fanny, Zander, and their young son blow through wherever they happen to be like a tornado, but for a film about bickering couples, Bell keeps noise and chaos minimal. Her Alice and Helms’ Noah are the grounded ones here, their conversations quiet but often funny. (When she complains that she has no hand-eye coordination, he says, “You are very good at hacky sack.” “You’re just saying that,” she responds.) Alice is even soft-spoken on camera, particularly when she remarks that Noah keeps his glasses on for cunnilingus. (“My vagina felt inspected.”) Much of the humor is aimed at New Age types, with mentions of moon-chanting groups and “gut-extracting” performance art. And if you’re a snorer, don’t let your partner get any ideas. “I took to putting a pillow over his face,” Cybil says during an interview.

Then there are the tender parts. Bell lets her camera linger a few beats longer than you’d expect to take in Alice and Noah hugging after a tough talk. Harvey has a tiny, surprising moment when he defends his wife while Vivian is pushing her to talk about something she’d rather not discuss. The film does get cheesy, and at one point too triumphant, but the finale involves some delicious trickery aimed to run Vivian out of town. It’s a grand gesture in a story that focuses mostly on the small things that build a relationship, such as when a flustered Alice says, “I listened to Widespread Panic for you!” But in a farce about marriage, you knew it was coming.

I Do…Until I Don’t opens Friday at the Angelika Film Center, Landmark E Street Cinema, and Landmark Bethesda Row.