Ruth Patchett is a frumpy, disheartened housewife who feels undervalued by her self-absorbed husband, Bob, an accountant. Bob is infatuated with Mary Fisher, a glamorous and successful romance novelist. Ruth's world comes crashing down when she discovers Bob is having an affair with Mary. Devastated by this betrayal, she reaches her breaking point and vows to turn the tables on both her unfaithful husband and his lover. Ruth meticulously begins to dismantle Bob's perfect life, targeting his career, his assets, and his relationship with Mary.

As Ruth's plan unfolds, she employs her wit and strategic thinking to expose the flaws in Bob and Mary's seemingly ideal existence. She secures a job and starts climbing her way to independence while methodically executing her revenge. Ruth's transformation from a submissive housewife to a determined woman on a mission leaves a path of destruction in its wake, revealing the absurdities and vulnerabilities of those who underestimated her.