A group of scientists with Operation Deep Freeze discover frozen prehistoric trees and other specimens in the Antarctic dating back to the first Ice Age. They collect samples of each for further study and load them aboard their C-47 military transport.
The dull, workaday life at the Navy weather station base on Gow Island in the South Pacific is interrupted by that very same C-47 transport aircraft. On a routine approach for refueling, the transport experiences unusual trouble and suddenly crash lands on the island's single airstrip, destroying its control tower and the island's only two-way radio. The stricken aircraft also blocks the runway, preventing its further use. Lieutenant Charles Brown (Eisley) is in command of Gow's weather station. He, Navy nurse Nora Hall (Van Doren), and biologist Arthur Beecham (Walter Sande) reach the wreck only to find that seven scientists and crew aboard the cargo aircraft when it left Antarctica are now mysteriously missing. The only one found aboard is the transport's pilot, who is traumatized and in a state of shock, unable to speak.
Unloading the prehistoric cargo from the crashed C-47, Dr. Beecham recommends planting the trees to ensure their survival in the island's tropical conditions. Somewhat later, Gow Island's bird population becomes disturbed by something unknown. At the same time, the weather station's scientists try to figure out a connection between this event and a corrosive residue that begins turning up at various island locations.
It slowly becomes clear that the planted prehistoric trees have quickly grown into acid-secreting, carnivorous monsters that move about Gow Island at night, at will. They reproduce fast and eventually cut off the island with their growing numbers and nocturnal assaults on Gow's native islanders. Brown has to hold together his dwindling Navy personnel and the coterie of scientists and civilians while figuing out a way to stop this prehistoric menace. The Navy personnel's only available weapons prove largely ineffective against the tree monsters.
Eventually, the weather station is able to restore radio contact with the mainland and ask for help. In response, the military sends in multiple aircraft strikes from their nearest base. Fighter jets drop both napalm and fire air-to-ground missiles at the slow-moving night monsters, blowing then up or setting them ablaze. As a result, the prehistoric threat to Gow Island's surviving personnel is quickly eliminated.
How many people are on the plane that crashes?
One