Dr. Jonah Fisher and Dr. Sadie Shaw have been academic rivals for 15 years. Since meeting as undergraduates in Literary Studies at Eastern Sydney University (ESU), they have clashed in seminars and argued about nearly everything. Jonah, the son of Professor Christian Fisher, a powerful scholar at ESU, developed a crush on Sadie early on but buried it when she made clear she couldn't stand him. Sadie, who lost her mother to cancer at 16 and was abandoned by her father, fought her way into academia from poverty, raised by her older sister Chess (Francesca Shaw), a lawyer. For Sadie, Jonah represents institutional privilege: the well-connected son of a man who once dismissed her research into popular fiction as "specious, frivolous, and pointless."
Their rivalry is punctuated by six ceasefires. They tie for the University Medal as undergrads, accidentally move into the same Sydney share house, graduate with their PhDs in the same ceremony, and are hired to co-teach at Bass University, where their combative lecturing style produces extraordinary student reviews. The first five truces break; the sixth holds.
That sixth ceasefire arrives on Jonah's 32nd birthday. He returns from a dinner where his father revealed that Jonah's sister Fiona's husband has left her for a secret second family. Sadie finds Jonah slumped at the kitchen table, and they hold hands, agreeing to stop fighting. The next day, a permanent Lecturer position is listed at Lyons University in Hobart, with desired specializations in early modern drama (Jonah's field) and popular fiction (Sadie's). For Sadie, who has spent years in the precariat, the insecure class of adjunct scholars cobbling together casual work, this is a once-in-a-lifetime opportunity. Her PhD research focuses on eucatastrophe, a term coined by J. R. R. Tolkien for the sudden joyous turn when something good happens against all odds, and the listing feels like her own. For Jonah, the job would place him near Fiona. Both are short-listed. Jonah's nervousness undermines his interview, while Sadie delivers hers with composure. A few days before Christmas, Sadie gets the job.
While reviewing her contract, Sadie discovers a partner hire clause: If she has a partner who is suitably qualified, the university will consider hiring them too. The provision requires a statutory declaration, meaning the partnership must be legal. Sadie proposes marriage to Jonah, framing it as a business arrangement. Their living situation would not change, the declaration would be technically truthful, and Jonah would get a job near Fiona. She appeals to Jonah's love for his sister and invokes eucatastrophe, calling the arrangement something good in the middle of a nightmare. After initial resistance, Jonah agrees. They buy cheap rings, settle on "darling" as a pet name, and negotiate with university HR, who ultimately offer Jonah a contract.
To sell the ruse, they tell everyone they realized they were in love all along. They endure a hostile dinner at the Fisher family home and video-call Fiona, who bursts into tears of relief. But Sadie cannot bring herself to tell Chess. The night before the ceremony, she finally confesses, and the conversation becomes a devastating fight. Sadie tells Chess that being loved by her is "exhausting," that Chess loves her "too much." Chess goes silent, and Sadie leaves.
The wedding takes place the next afternoon in a park under a fig tree. Jonah's brother Elias flies in from Germany; their housemates serve as witnesses. Chess does not come. The ceremony is brief, and Sadie is visibly shattered. Afterward, Jonah persuades Sadie to spend the night at his parents' empty house. He carries her to bed when she falls asleep on the couch and wakes to the sound of her weeping through the wall. At the airport the next day, Chess appears at the last moment to warn Jonah she will ruin him if he holds Sadie back. She tells Sadie she loves her but needs time alone. At the gate, Jonah puts his arm around Sadie, and she clings to his hand.
In Hobart, they discover their hotel room has only one bed and share it out of exhaustion. From then on, Sadie wakes every morning sprawled across Jonah's back despite pillow barricades. Their new life is overwhelming: a shared office the size of a cupboard, 52 lectures to co-write from scratch, and a department head, Lachlan Petrovski, who openly favors Jonah while treating Sadie with contempt. Sadie befriends Julia Scott-O'Connell, a historian who becomes her ally and union representative. They settle into an apartment in Bellerive, near Fiona.
Every week, Sadie sends Chess a letter begging her to call. Chess never replies. Jonah has acknowledged to himself that he is in love with Sadie but resolves never to tell her. Sadie begins craving his closeness but holds herself back, terrified that attachment will destroy her when the marriage ends, as she believes all her bonds eventually do.
Petrovski shelves Sadie's popular fiction unit and assigns them another crushing teaching load. Then a letter arrives from Chess explaining she has taken a leave of absence to figure out who she is when her life doesn't revolve around caring for Sadie, adding that Sadie can call if she truly needs her. Sadie misreads the letter as Chess cutting ties forever.
On Sadie's 32nd birthday, Chess sends wine but does not call. That night, Sadie tells Jonah they need to discuss "how this ends," insisting she is a burden and that everyone she loves leaves eventually. Jonah warns her that what he is about to say cannot be unsaid, then confesses he has loved her for 15 years. Sadie asks him to kiss her. He does, and they consummate their marriage. Afterward, Sadie tells him she was already in love with him when she proposed.
Their happiness is shattered weeks later when the university announces "Renewniversity: Phase Three," a restructuring plan. One component raises teaching loads by 10 percent, eliminating many casual staff positions. Another collapses the department's two Level B (lecturer-rank) posts into one, forcing Sadie and Jonah to compete for a single job. Sadie realizes the university used partner hire to extract maximum labor from both of them before cutting one loose. Jonah immediately tells her he will not fight her for the position.
Sadie refuses to accept this. She and Julia launch a media campaign portraying them as star-crossed academics torn apart by institutional cruelty. For the legal fight, Sadie finally calls Chess. Chess arrives in Hobart, and the sisters reconcile in a tearful conversation that reveals a painful miscommunication: Chess never intended to cut Sadie out but was trying to give her space to grow independently. Both realize they have been suffering in parallel, each believing the other no longer wanted them.
Chess buries the university in legal red tape while the media campaign generates public pressure. The university backs down, calling the elimination of Jonah's position a "clerical error." Chess's legal work also overturns the casual-staff cuts, protecting precariat workers across the institution. Professor Fisher, enraged that his son's job was threatened, turns his considerable influence against Petrovski.
In the epilogue, months later, Sadie and Jonah sit on the couch in their pajamas, comfortable and content. Chess visits regularly and has found Fiona an excellent divorce lawyer. The gold finish on Jonah's wedding ring is wearing off, and he suggests they buy real ones. Sadie proposes a real wedding, one where both sisters are present, where they choose each other "properly, and forever, instead of kind of doing it by accident." Jonah, in tears, says yes.