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.
Sharon's parents visit from Ireland and have a strained introduction to Rob. More health complications create stress for them both, and Rob's secret friendship with Chris explodes in his face.
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.
A heavily pregnant Sharon picks Rob up at the airport after a trip to Boston and tells him she has invited an old friend from Ireland to be her maid of honour. Rob decides to ask his fiancee's brother to be his best man, but Fergal has more important things to worry about - his wife has left him and taken their children. The bride and groom later split up to enjoy their hen and stag nights, both of which spiral out of control.
Turbulent lovers Rob and Sharon arrange an ill-considered party to enable friends and family to meet their newborn baby. Unfortunately for Sharon, the gathering coincides with a disturbing revelation about her father's health, a visit from Rob's mum, and an unfortunate incident with the family dog.
A sexually frustrated Rob is disappointed when Sharon's psychologist prescribes antidepressants, and not more sex, as a treatment for post-natal depression. However, an outlet for his pent-up libido arrives at work in the form of an attractive new French colleague Olivia, who he quickly engages in what starts out as harmless flirtation. Meanwhile, now that she has been suitably numbed, Sharon finds herself capable of contemplating the world of mother-and-baby classes, but when her only 'mum friend' Sam goes AWOL ahead of a session, she is forced to deal with the dreaded 'mombies' alone.
Sharon decides that she and Rob should inject some passion into their love life. When her advances don't go to plan, Rob suggests a weekend break in Paris. While Fergal looks after the kids, Sharon develops an appetite for a holiday drink.
As Rob and Sharon celebrate a tainted wedding anniversary, Fran and Chris are drifting further apart. Elsewhere, Dave's flourishing love affair with Catherine - a high achiever he's met through AA - is gathering momentum.
Sharon decides to return to teaching but her meeting with the head mistress becomes more of an outpouring of her grief. Meanwhile, Rob feels awkward around Olivia due to her indecent proposal and Dave's life spins out of control following his split with Catherine, and Sharon's brother Fergal fails to repay the money Rob secretly lent him.
Rob has told Sharon about the Olivia situation, but the news is badly received, and she throws him out of the house. Unfortunately for him, the first person he can turn to is Dave, who is in the middle of an epic post break-up bender. Sharon tries to reach out to Rob, but after a brief reconciliation it turns into a major argument which sends the pair into a spiral of bad behaviour. For Sharon it's a night out with 'party pal' Kate, and for Rob it's the surprise decision to have a drink.
Rob picks up where he left off last time, with an unexplained receipt for the morning after pill in his hand and a lot of questions for Sharon. Too drunk at the time to remember what she did, Sharon dodges Rob's interrogation and goes to see Nico perform with his band to find out the truth. Will she tell Rob what actually happened? The issue is unexpectedly forced when one of the kids has an accident.
Rob and Sharon are still on shaky ground with each other and face challenges in their work lives too. Sharon returns to teaching, leaving Rob looking for a new job while in charge of the school run, where he is immediately embroiled in playground politics. Elsewhere Sharon's brother Fergal is moving to Spain, and while Rob goes to see Dave recovering in rehab, could his own addiction issues be rearing their ugly head?
Rob and Sharon find themselves facing financial difficulty after hearing bad news from the estate agent. Rob's at an all-time low and tries to battle his weight gain by joining a gym. Sharon's friend Fran is also dealing with vanity issues and tries to kick start a new life with plastic surgery. A last ditch attempt to resolve their money problems results in Rob being humiliated - will it lead him crawling back to his old job?
Seemingly back in the swing of a fully functioning relationship, Rob and Sharon receive a very surprising dinner invitation from estranged couple Fran and Chris. Meanwhile, Fergal travels back to London to give an update on his unsatisfactory family life in Spain. Sharon has a check-up with a less than empathetic doctor where it's revealed that she's now pretty low in the egg department. And Rob's dark secret is uncovered by Chris.
Rob returns to his job at Braeband stating he is just back from 'holiday in Canada', while bad news pulls Sharon back to Ireland. With Sharon away, and left home alone to look after the children, Rob's life continues to spiral out of control. Unhappy with the situation at his family home Chris decides, in typical style, to confront his nemesis.
Rob and Sharon are in Ireland to say goodbye to Sharon's dad. Rob's utterly irrepressible mum Mia travels from America to pay her version of respects. With Fran reeling in shock, and Rob still unable to find the right time to talk about his almost-secret collapse, all roads are leading to a dramatic series finale.
A new acquaintance becomes increasingly friendly with Rob, while Sharon dabbles in a new hobby.
Rob's newly religious sister Sidney visits from the US, and a child's accident at school reveals a surprising teacher-pupil rapport to Sharon.
Sharon and Rob decide to get on a fitness drive. When Sharon visits her less-than- sympathetic local GP it dawns on her she's not in the peak condition she imagined.
Rob is pretty unenthusiastic about the prospect of celebrating brother-in-law Fergal's 40th birthday. Sharon comes face to face with her mum's new man, while Fran and Chris drunkenly party with their new partners.
Sharon is unsettled by a strange moisture patch at school, while Rob's big boss visits London and takes a close interest in his career. Fran and Chris make a major decision.
In the final episode, Sharon and Rob arrive in Boston for a family holiday only to receive some tragic news about Rob's mum, Mia.
