Terry believes he's an ordinary married man stuck in a predictable routine when his life is suddenly upturned. During his morning commute he is staggered to spot his exact double. It's Gerry, the twin he never knew he had. Thrilled, Terry wants to search out the birth family but Gerry isn't keen. He is proud of his upmarket, sucessful adoptive family and has a glamorous girl-friend. Terry is quickly enamoured of her, too.

When he excitedly tries to tell his eccentric wife, Gudrun, about discovering Gerry, she doesn't seem to want to hear his news. Annoyed, he begins his search in secret. What he finds is difficult to adapt to but the Pandora's Box, once opened, can't be shut again. It plunges him into increasingly bizarre situations.

Is Terry far more quirky than imagined, or unworthy of his successful twin? And when he commits to sharing all he's discovered with his wife, what does he find she's Gudrun been hiding all along?