A simple question has been on Kieran McKay’s mind for years: is there a link between the two extensive cave systems of Nettlebed and Stormy Pot on the South Island of New Zealand? Their search for the answer takes him and his team one thousand metres below the ground. Down there, where it makes more sense to measure distance in hours and days rather than in metres, the cavers close in on what they refer to as the “connection area” from both sides—the area where, according to their calculations, the two caves are likely to meet. The way there is stony, wet, cold and dirty. But the thought of discovering this link, and with it possibly the largest cave of the Southern hemisphere, pushes the adventurers on, even though they are up to their necks in water more than once in the underground passages and halls, and the expedition takes them to their physical and mental limits.