Adventurer and naturalist Steve Backshall embarks on one of the most dramatic and dangerous expeditions ever filmed by a BBC crew. His mission: to explore Venezuela's tepuis — ancient, sheer-sided mountains, lost worlds cut off from the jungle below. The second episode picks up where episode one left off with Steve and the climbing team halfway up the unclimbed, sheer-sided face of a remote tepui, about to make one last desperate attempt to reach the summit. It is then on to a new tepui and the second stage of the expedition. Joining up with a team of elite Italian cavers, Steve ventures deep within a tepui — inside a newly discovered cave. Within this dark underworld, the team encounter strange creatures, ancient mysteries and the raw geological forces that give the tepuis their unique shape. But nothing can prepare them for an attempt to forge a path into unexplored areas of the cave — a dangerous mission of intense claustrophobia and nerve-shredding tension. And then to end the adventure, Steve reunites with the climbing team for a spectacular finale: an epic abseil alongside the Angel Falls — the highest waterfall on earth.