Everyone needs a holiday — but who knows where it will lead? Sophie and Andrew are looking for relief from the daily grind — if not each other — so when a friend puts them in touch with William and Beth, newlyweds looking to swap houses for the summer, it seems a solution of sorts. They find themselves in a stylish Connecticut home, a stone's throw from New York, while William and Beth take over their lived-in family house in South London, ideal for spending time with William's teenage sons. The weeks away work an unexpected magic for Sophie, who begins to find a sense of happiness... but Beth has no such luck and, no longer the centre of William's world, grows increasingly miserable. And so the two marriages — one crushed by the weight of years, one shiny and new — slide into reverse. But who can foreseen the dramatic consequences of their lives, and hearts, intertwining? This innocent holiday might just prove devastating...