Lawyer Sienna can hardly believe her luck when her long-time partner and dream man Oscar proposes to her. Nevertheless, Sienna hesitates briefly because, unbeknownst to Oscar, Sienna is already married to her childhood sweetheart Tyler. Years ago, she left him head over heels after Tyler cheated on her. But on paper, they are still wife and husband. So Sienna travels to Cornwall to persuade Tyler to sign the divorce papers. But he wants something in return from his former partner. He is currently fighting for custody of his daughter Ivy, who was born out of the affair. Ivy's mother Naomi has since died. Sienna is supposed to pretend that she and Tyler have a happy marriage so that Ivy doesn't have to move in with her grandmother in the USA.