Robert, a young novelist, goes to meet his friend Alex for lunch. When Alex asks about his latest work, they get into a discussion of what makes up the perfect love story. The conversation develops into a discourse on the nature of love: its representation in art versus their real experiences.
They talk about love at first sight. They talk about tragic romance as opposed to living happily ever after. They talk about great romantic texts: Romeo and Juliet, Tristan and Isolde, and modern romantic texts: Titanic, Once, The Notebook.
Throughout their conversation Robert relives a series of memories, all concerning his relationship with Katherine; a beautiful dancer. The memories play out in reverse order, from last kiss to first meeting. With each new memory we understand more of their relationship and how it has shaped Robert's ideas about love.
Ultimately we are led to an understanding of Robert and Katherine's separation, something the present Robert has yet to make peace with.