The couples gather at a weekend retreat - but this is no relaxing getaway. Over the course of the weekend, relationship experts John Aiken and Desiree Spierings will dig deep into the causes of their problems to plan strategies for the couples over the next eight weeks. Each of the couples faces different issues but share a discontent at the state of their relationship. For some, this experiment is their last chance. Paul and Alison have been married for 29 years, but their lack of intimacy is so profound that Alison can't look Paul in the eye. 25-year-old Carla moved from Italy five years ago to marry Domenic, but their volatile arguments have her doubting their relationship will survive. 40-year-old Steve and 36-year-old Paula are finding that being the parents of two young kids is putting unbearable strain on their marriage, while Laney and Darren try to juggle the stress of bringing up a family with running a busy plumbing firm.

Two weeks into the eight-week experiment and the experts focus on the couples' communication styles - both verbal and non-verbal. John takes the couples to an archery range. This may seem like tempting fate, but he wants to show them how focusing on the positives rather than the negatives pays dividends in both archery and relationships. Desiree lines up an unorthodox communication lesson for Alison and Paul in an Aikido studio, where they learn that the principle behind the martial art - 'yield to win' - is also at the heart of successful relationships. But when Desiree discovers that it's a challenge for Alison to even hold Paul's hand, the scale of the barriers the experts face becomes clear. Paula and Steve are shocked to learn from Anna-Louise that 85% of all communication is non-verbal, and they put the research to the test by identifying happy couples randomly from their body language, and discovering their secrets for a happy relationship.

As the experiment passes its halfway mark, the experts focus on sex and affection, which is proving a major stumbling block for many of our couples. John introduces the volunteers to the concept of 'love languages', and they learn that everyone likes to express and receive affection in one of five different ways - time, touch, talk (or words of affirmation), tokens and tasks. Both Laney and Paula have a love language of talk, but their husbands are unable to express the words of affirmation they need. An intervention by John sees Darren and Steve pushed outside their comfort zones. Darren also discovers that doing the housework is an unexpected aphrodisiac. Desiree introduces Darren and Laney to foreplay maps, and they quickly discover that both have a lot to learn about what excites the other. Meanwhile, Dom's continual lateness puts his relationship with Carla at risk. An evening swing dancing session with Anna-Louise and John gives them hope for the future.

The end of the eight weeks is in sight, but the couples still have many hurdles to overcome. Alison apologises to Paul for an affair and reveals the true story behind it. He has to make a decision that will decide the future of their relationship - will he forgive her or not? After the emotional intensity of the apology, Paul takes time out with the other men, as John organises a BBQ to deliver some home truths about the emotional differences between the sexes. To encourage the couples to lock lips, John organises a kiss-in for charity at a central Sydney mall. Inhibitions crumble as the couples show off their newfound sexual chemistry. As the experiment reaches its conclusion, the couples write each other love letters, which are displayed and read in a public gallery.