Explorer Levison Wood is in Panama, on the final leg of his attempt to walk from Mexico to Colombia along the length of Central America. And now he must cross the most dangerous stretch of jungle on Earth - the Darién Gap - to reach Colombia. One of the world's last wildernesses, the Darién Gap is home to drug-runners and militia and has defeated explorers for decades. And before attempting to walk through it, Levison explores an uncharted vampire bat-infested cave, and witnesses the engineering marvel of the Panama Canal and the modern metropolis of Panama City, before staying with indigenous tribespeople in villages deep in the jungle.