It is such a romantic movie which tells about the two close friends, Emma (Anne Hathaway) and Dexter (Jim Sturgess). Emma and Dexter are so close in their friendship. They attended in the same university. They have had a promise that they would be always in friend forever. Then, after graduated from University, they make an agreement that they must meet at each 15 July.
Actually, either Emma or Dexter has already had a feeling each other. But with the agreement that they have to keep the relationship in friendship, make them never reveal what they feel to another.
For Dexter, 15 July is St. Swithin day, the myth day for him whereas when its day is rain so that the 40 days later will never change. Otherwise, Emma is not believed in such a faith. She prefers to make this day special for keeping the friendship made.