The four couples fly to Thailand to meet their new partner for the first time. Within minutes they face a decision that throws everything into question, including the future of the experiment.
This week the newly switched couples Rachel and George, Nikki and Tony, Gemma and Simon, and Michelle and Tom head out on their first dates together - where they open up about their failures at home and hopes for the experiment. The switched couples then face their first exercise. Each person must witness moving, gut-wrenching revelations and confessions from their real partners, which they have never had the courage to say before now, sparking high emotions and fireworks.
The switched couples go deep as they act out past arguments they've had with their partners. They also open up about their sex lives. And Tom smartens up his act with Michelle.
As the bonds between the switched couples strengthen, therapist Lee Valls drops a bombshell when he reveals pictures of what their real-life partners have been up during their time apart. Some of the photos send shockwaves across the group. In particular, a photo of George's wife Michelle - who George thinks is sunbathing naked with her switch partner Tom. The next day, the men meet face-to-face for the first time and the women do the same. With some still angry and desperate for the truth, it quickly becomes an emotional showdown.
With their time in Thailand drawing to a close, the four couples prepare to be reunited. How do they feel about being back together after spending two weeks with another?
In the final programme, all four couples return home, where they must try to put everything they've learned from the switch experiment into practice in their day-to-day lives. Each couple will then meet therapist Lee and relationship coach Vena to answer one, final, life-changing question - do they want to stay together or part ways for good?