The couples focus on repairing toxic communication styles & learn non-verbal communication is as important as what is said. But change is hard, & for Dom & Carla, memories of their honeymoon fuel a major dispute.

Sex takes centre stage as the couples explore passion and intimacy. Darren and Laney revitalise their relationship with a trip to the trapeze school, while Alison's 50th birthday party leads to an unexpected breakthrough.

As the experiment ends, an apology from Alison could make or break her relationship with Paul. Inhibitions are lowered during a kissing contest in a crowded mall, and the surprising final scores are revealed.