Summary Boyd and the other Cubes attend their first live pro fight. They start to truly understand what they have signed up for. The brutality of the sport is inescapable up close - humbling, scary, exhilarating. We meet Jeanette, a Cube, and her fiancée, Mike, a former pro who goes into the ring again after suffering a serious head injury. Mike wins - giving the cubes a sense of the sport's unpredictability, as well as the letdown of loss, the high of winning. They also start to get a sense of the sport's camaraderie. We meet Sebastian, an English teacher, who has never fought before but wants to get out of his comfort zone. The final group of 30 Cubes starts their training. Peter tests their resolve with punishing sessions. United by pain and drive the group begins to bond. But then the first Cube quits.

• Documentary