Moving to London is supposed to be a new start for Abby Nichols and her husband Rob, but with no friends or family around her, she feels increasingly isolated. Struggling to find a teaching job, she is grateful when she meets confident and full of life, Sienna, everything Abby could wish for in a friend.

But one night, Abby makes a huge mistake. During dinner at Sienna’s house with their husbands, when they have all been drinking – every one of them trying to escape from different things – someone mentions the reality TV show Wife Swap and Sienna jokes that they should do it for that evening, just to have some fun. After some discussion, the four of them all agree to do it under the condition that nobody is unfaithful.

But what starts off as a harmless game soon has serious repercussions for Abby and Sienna, and it’s not long before they both start to question their friendship and their own marriages…