Rosie's father dies. Alex attends the funeral, where he reconciles with Rosie. At the same event, Greg behaves immaturely, causing a scene. This later prompts Alex to write Rosie a note saying that she deserves better and that he can be that better man. However, Greg intercepts the note and hides it from Rosie. Later, Rosie discovers that Greg is cheating on her and kicks him out. While disposing of his things, she finds the letter from Alex. She calls him, but discovers that Bethany is living with him now and that the two are engaged. They invite Rosie to be the "best man" their wedding.
Rosie plots to interrupt the wedding, but fails, as the church ceremony is over by the time she arrives. At the reception, Rosie gives a speech, telling Alex that she loves him as a friend. Her daughter, Katie, brings a friend named Toby with her to the wedding, in a friendship that is reminiscent of Rosie and Alex when they were children. During a dance, Toby suddenly kisses Katie, but Katie pushes him away and runs outside. Rosie and Alex follow her. Alex counsels her and tells her to follow her feelings with Toby or she might regret it, alluding to how he felt about Rosie. After a moment, Toby finds Katie and apologizes for what he did. As he asks her to forget what just happened, Katie interrupts him with a kiss. In that moment, Alex learns that Rosie does not remember the kiss that they shared on her 18th birthday. He realizes that he had been mistaken in interpreting her desire to forget that night as her wanting to stay platonic.
Years later, Rosie finally fulfills her ambition to start her own hotel. Alex is her second guest. When he arrives, he tells Rosie that he ended his marriage with Bethany, and shares with her a recurring dream he has had about the two of them being together. Finally, they kiss.