City girl Anna (Amy Adams) and her boyfriend Jeremy (Adam Scott) have been in love for four years and jointly apply to buy a high-end home in Boston's top luxury community. Anna thought Jeremy was going to propose to her, but after being disappointed, she followed her father's advice and flew to Dublin, the capital of Ireland, intending to propose to Jeremy, who was attending a medical conference in Dublin on February 29th of the leap year in accordance with Irish tradition. Unexpectedly, the plane encountered turbulence and was forced to land in Cardiff, Wales. Anna hired a boat from Cardiff to sail to the Dingle Peninsula in Ireland, and stayed at the seaside hotel of the local youth Declan (Matthew Goode) in a miserable state. Declan agreed to drive Anna to Dublin the next day. Along the way, the two disliked each other and quarreled endlessly. During the dispute, they encountered hilarious events such as car breakdown, heavy rain, delays, and pretending to be a couple staying in a farmhouse, but this pair of enemies also got to know each other in constant friction and gradually developed feelings. February 29th finally arrives. To whom will Anna entrust her heart?