Tancrède Melet and Julien Millot are masters in the art of high lining. Together they are alone, balancing on a thin lifeline that is pulled taut between two vertical faces of the mountain. The French duo often takes steps to improve their skills, but on this trip they make an important stride - walking 'untethered' without a leash. Suspended thousands of meters above sea level and free of any attachments, Tancrède and Julien are able to try something new as they part with their lifeline and BASE jump into the void.