When Irish schoolteacher Sharon meets American advertising executive Rob in a London bar, it doesn't take long for them to end up naked. After a sweaty, week-long fling, Rob returns to the States and his old life. A surprise call from Sharon with some "news" prompts him to fly back to London to help figure things out.

Sharon faces the reality of having a giant new roommate in the form of Rob, the man whose child she happens to be carrying. As Rob tries to fit himself into his new London life, he connects with an old school pal, Dave, who's evolved into a delightful scumbag, and meets Sharon's feral brother Fergal - all while trying to cook up a proposal to help Sharon feel better about their situation.

Sharon's hormones plague her with waves of horniness, sadness and a host of other fears. Rob begins a friendship affair with Chris, husband of Fran, the insufferable friend Sharon loves to hate. Sharon has a chance meeting with an old flame.

Still getting to know each other, Rob and Sharon continue to enjoy a vigorous sex life. Sharon’s parents visit form Ireland and have a strained introduction to Rob.

Sharon and Rob plan their wedding while Rob plans a surprise birthday party for Sharon. Rob is fired via Skype by his Boston bosses and begins searching for employment in London.

A very pregnant Sharon picks Rob up at the airport and tells him she’s invited an old friend from Ireland, to be her maid of honor at their impending wedding. Rob decides to ask Sharon’s brother Fergal to be his best man.