In Ireland, Rosemary Muldoon (Emily Blunt) has loved eccentric Anthony Reilly (Jamie Dornan) since she was a child, but Anthony treats her as if she was a sister. His father, Tony Reilly (Chistopher Walken), tells Rosemary she'll have to wait forever if she's waiting for Anthony to make a move.
Tony, who fears that his son will never get married and have children, threatens to pass the family farm down to his American nephew Adam (Jon Hamm). Just as Anthony tries to work up the nerve to ask Rosemary to marry him, Adam, who goes after what he wants without hesitation, arrives in Ireland. Adam immediately begins to woo Rosemary. In spite of the setback, Anthony doesn't give up on Rosemary.