Renowned caver Bill Stone is on a lifelong quest to go deeper beneath the earth than any human has ever ventured. Deep in the unexplored depths of Cheve Cave in Mexico, his goal is to set a new world record by finding a passage beyond a depth of 7,208 feet, proving once and for all his theory that Cheve is the deepest cave in the world. The expedition has been compared to climbing Everest - but in reverse. The three-month underground journey is a dangerous and highly technical adventure through over 12 miles of tight, twisting passages. The pressure to conquer the cave will push Bill and the team to the absolute limits of survival and sanity.