Robin Lightfoot (Hugh Bonneville) is a confirmed bachelor with a successful architectural business. One day however, he wakes up to find himself in a parallel universe where he is married to Leslie (Josie Lawrence) and has two children: Ned and Maxine.

Robin discovers that the version of Robin in this universe is a horrible man - a cad, a womanizer, a swindler and possibly even a murderer. The only person who believes that he comes from a different universe is his 'son' Ned, because he reads comic books set in parallel universes.

While Robin tries to deal with adjusting to married life, he must also come to terms with the other differences in this new universe: he is living in a world where the North-East of England is economically prosperous while his home county of Surrey is depressed; Tony Blair is the leader of Conservative party but the power is in the hands of the Lib Dems; and a world in which Arthur Smith is a children's entertainer.