Gorgona Island is chosen by the Colombian government as a prison site, because of its shark-infested seas, impenetrable jungle and deadly snakes.

On the tiny Caribbean Island of Providencia, 400 miles from Colombia's Atlantic coast, a young female black crab is about to undertake the biggest mission of her life; to escort her 80,000 eggs from her mountain top home, on a 2 mile hike to the coast.