An American man and an Irish woman fall in love with each other in London while navigating the choppy waters of their increasingly complicated lives. Scorching chemistry, instant pregnancy and genuine disaster provide the foundation for a relationship full of ups and downs.

Sharon faces the reality of having a giant new room-mate in the form of Rob, the man whose child she happens to be carrying, and her brother Fergal doesn't make life any easier. Rob also meets up with an old school friend and comes up with a proper proposal to help Sharon feel better about their situation.

As pregnant Sharon's hormones plague her with waves of different emotions, she has a chance meeting with an old flame, which leads to dinner. Meanwhile, Rob struggles to generate advertising business, since he has very few contacts in London, and begins a clandestine friendship with Chris, who is married to a woman Sharon can't stand.

Rob and Sharon continue to have a very vigorous sex life. Sharon's parents come over from Ireland and meet Rob for the first time. Some new health complications jeopardize Sharon's pregnancy and cause stress for the couple.

As the couple plan their wedding, Rob decides to throw a surprise birthday party for Sharon - but also finds himself searching for a new job after his Boston bosses fire him during a video call. To make matters worse, the groom's mother (guest star Carrie Fisher) reveals a big secret he has been keeping from his fiancee.

Sharon picks Rob up at the airport following his to Boston and she informs him that she's invited an old friend from Ireland, to be her maid of honor. Rob decides to ask Sharon's brother Fergal to be his best man and finds out that wife has left him and taken their children with her. Rob and Sharon go on heir stag and hen nights, both end up out of control.