Since the sixties generations of explorers have attempted to link two giant caving systems under the Mount Arthur range in New Zealand's South Island. Their goal, to discover the largest and deepest through-cave system in the Southern Hemisphere. Now gathering on the years of experience and knowledge of the caves, a caving team led by the driven Kieran Mckay set off for one last bid. Splitting into two teams they will work towards each other to where they believe the crucial connecting point of the tunnels exists. They will need to spend one week over 900 metres underground.