Guam is under siege! Not by rebels or members of a hostile army, but by a ten-foot-long serpent - the Brown Tree Snake. Since its arrival, probably from New Guinea aboard a U.S. cargo ship, the voracious predator has wiped out most of the island's bird population. National Geographic follows scientists as they battle to save endangered fruit bats and the last of the island's Mariana crows. Meanwhile, animal control personnel battle to keep any one of the island's 1 million brown tree snakes from invading other islands vulnerable to a SNAKE INVASION.