The film initiates with an intimate but comically charged moment, setting the tone for a narrative that delves deeply into the complexities of middle-aged marriage and family life. As the story unfolds, we meet Pete, played with affable charm by Paul Rudd, and Debbie, portrayed by Leslie Mann with a blend of strength and vulnerability. Their relationship is put to the test in a myriad of ways, particularly during an ill-timed moment when Pete admits to using Viagra, causing a rift between them. This incident not only highlights the couple's declining intimacy but also shines a light on the core of Debbie's midlife angst—turning 40.

In the five years that have passed since the events of , Debbie has ventured into the business world with her boutique store, employing the glamorous and seemingly carefree Desi, as well as the quirky Jodi. Meanwhile, Pete struggles with the viability of his record label, desperate to revitalize it by reuniting the band Graham Parker & The Rumour. The film deftly explores the financial strain on their marriage, echoing the universal fear of professional failure juxtaposed against personal commitments. As they grapple with these challenges, they're also navigating the tumultuous waters of parenting their two daughters, Sadie and Charlotte, each presenting unique hurdles as they edge into adolescence and childhood, respectively.

The couple’s decision to escape for a romantic getaway intended to rekindle their relationship reveals both their affectionate bond and underlying frustrations. A humorous interlude ensues as they indulge in marijuana cookies, leading to a hysterical conversation imagining inventive methods of murdering each other—a testament to the depth of unresolved tensions.

Debbie's conversations with friends Barb and Jason catalyze her determination to rejuvenate her marriage and family through a newfound commitment to exercise and familial bonding. Debbie takes charge and insists that Pete cease financially supporting his perpetually dependent father, Larry. Pete's failure to deliver this news convincingly to Larry underscores a recurring theme of familial obligations clashing with financial realities. Meanwhile, Debbie discovers, in a private moment with her gynecologist, that she is pregnant—a revelation she decides to withhold from Pete, adding further layers of intrigue to her already complicated life.

The subplot involving their daughter Sadie being bullied merges comedic and serious tones, showcasing Debbie's fierce maternal instincts. Her confrontation with the bully's mother, Catherine—played memorably by Melissa McCarthy—explodes into a laugh-out-loud conflict, perfectly illustrating adult pettiness. This sequence culminates humorously in a principal meeting where unexpected vulgar honesty exonerates Debbie and Pete.

Dramatic irony builds as Debbie seeks the truth about financial discrepancies at her store. Her suspicions are aimed at Desi, portrayed by Megan Fox as enigmatic and effortlessly charming. However, an eye-opening night out reveals Desi's hidden life as an escort, complicating Debbie's perception of her. The revelation that Jodi is the actual thief adds further complexity, highlighting themes of betrayal and forgiveness in personal and professional relationships.

The turning point arrives at Pete's birthday party, a scene ripe with emotional confrontation. Both Pete and Debbie face unresolved issues with their fathers, starkly illustrating generational tensions and unmet expectations. Larry's financial dependency and Oliver's emotional inaccessibility converge, forcing Debbie to confront her buried resentments. These layered dynamics render vivid the emotional struggles both characters face as they seek validation and connection from their parents. The film wisely allows Oliver a moment of vulnerability, offering advice that underscores the series of realizations leading to Debbie's growth.

The climax finds Pete in a moment of existential crisis, overhearing Debbie speak of her pregnancy. His flight on a bicycle underpins a metaphorical escape from unvoiced fears rather than a physical one. This misunderstanding leads to a physical altercation and an eventual hospital visit, where the family's collective need for reconciliation and understanding crystallizes. It is in this vulnerable space that Debbie and Pete confront their fears and desires, laying bare their anxieties about family expansion—that ultimately culminates in affirmation and acceptance, with Pete eagerly embracing the idea of a third child.

Subsequent to these revelations, life moves forward with renewed optimism. As Pete and Debbie unwind at a concert featuring Ryan Adams, they contemplate their future, hinted at with the possibility of a new opportunity to revive Pete's struggling record label. This ending, rich with quiet optimism, signals a reshaped vision of familial and personal fulfillment, echoing the film's overarching message: that life’s complexities can be embraced through communication, love, and the shared struggle of family life.

In conclusion, traverses the comedy and chaos of middle-age and parenthood, weaving an intricate tapestry of life's trials and tribulations. The multifaceted characters and their relatable struggles make for both a reflective and riotous examination of aging and familial dynamics, providing ample laughter, insight, and ultimately, reconciliation. The film closes with a post-credit ad-libbed sequence by McCarthy, leaving audiences with an unforgettable reminder of the joyous absurdity inherent in everyday life.