Successful real estate agent Anna Brady is growing increasingly frustrated with her cardiologist boyfriend, Jeremy Sloane, who still hasn't proposed after four long years. Determined to take matters into her own hands, she decides to travel from Boston to Dublin to propose to him on February 29, which is leap day. According to an Irish custom, if a woman proposes to a man on this special day, the man must accept.
However, Anna's journey takes an unexpected turn when her flight is diverted to Wales due to a storm. In her quest to reach Dublin, Anna hires a boat to Cork, only to be forced ashore in a charming small seaside village called Dingle. There, she finds herself at a local tavern, where she seeks the help of a grumpy innkeeper, Declan O'Callaghan. Initially resistant, Declan ultimately agrees to taxi her across the country for EUR500, after his tavern's future is jeopardized by a looming foreclosure.
As Anna and Declan set off in his old, beat-up car, their contrasting personalities become apparent. Declan mocks her designer Louis Vuitton luggage, affectionately dubbing it "Louie," and he doesn't hide his skepticism regarding the leap year tradition Anna firmly believes in. Their journey quickly becomes chaotic when a herd of cows blocks the road, leading to Anna stepping in cow dung while trying to assist. In a mishap while cleaning her shoes, she accidentally sends Declan's car rolling into a stream.
Their misadventures continue when Anna attempts to catch a ride with three travelers in a van. Ignoring Declan's warnings, she hands over her luggage, only to be left behind as they drive off with her belongings. After a chaotic chase, Declan demonstrates unexpected strength by confronting the thieves at a roadside pub, retrieving Anna’s bag but earning their eviction from the establishment.
At a railway station, the duo waits for the next train, which leads them to a scenic hike to the ruins of a nearby castle. Here, they engage in a light-hearted conversation about what they would save from a fire. Declan captivates Anna with an old Irish legend involving a woman who escapes with her true love from an unwanted engagement. While captivated by the story, they lose track of time and miss their train.
That night, they find shelter at a cozy bed & breakfast in Tipperary. To deceive their conservative hosts, they pretend to be a married couple, taking the surname "O'Brady-Callaghan." This charade culminates in an accidental kiss during dinner, igniting unexpected feelings between them. Though they share a bed that night, they cautiously sidestep acknowledging their growing emotions.
The next day brings another storm as they hitchhike down the road, leading them to take refuge in a church where a wedding is underway. Invited to the reception, Anna loses herself in the festivities and starts to rethink her commitment to Jeremy. Just as she and Declan lean in for a kiss, she suddenly becomes ill and collapses.
Upon finally reaching Dublin, a surprised Jeremy promptly proposes in the hotel lobby. Turning to share the moment with Declan, Anna realizes he has already walked away, leaving her to accept Jeremy's proposal. However, during a later engagement party back in Boston, Anna discovers that Jeremy's intentions were less romantic than she had hoped—he proposed merely to appease their building's co-op board.
In a bold move, Anna pulls the fire alarm during the party, reflecting on the 60 seconds concept she had discussed with Declan. As chaos ensues, Jeremy scavenges for electronic gadgets, revealing his lack of concern for Anna's feelings. This moment of clarity leads Anna to conclude that her life with Jeremy lacks meaning, and she seeks happiness elsewhere.
Meanwhile, Declan returns to Dublin and retrieves his mother's claddagh ring from his ex-fiancée. Later, Anna finds her way back to Declan's tavern in Dingle. There, she confesses that she has ended her engagement to Jeremy, expressing her desire to be with Declan. Expecting rejection, she is caught off guard when Declan returns, ready to give her his mother's ring, and he proposes to her on a cliff, overlooking the sea.
With a joyful heart, Anna accepts his proposal, setting the stage for an adventurous journey together, leaving their destination to fate as they drive away in Declan’s car.
