S1, E4: Mark O'Shea travels to Florida, to investigate a spectacular comeback by nature's great survivor. The crocodiles outlived the dinosaurs, but in the 1970s one species, the American Crocodile, went to the brink of extinction. Now the beast is back, and O'Shea wants to know the secret of its unique recovery - a quest that takes him on a night hunt through the eerie canals of a nuclear power plant.