When a pilot crashes into an alien ship, he unwittingly unleashes a giant, highly poisonous spider on the native people of a small island near Guam. The doctors in Guam, not knowing the spider exists, are baffled as to what's causing so many of the native people to die, and so send an expedition to the island to discover the cause. The group is led by marine captain Valentine, and includes the pilot who flew them there, the doctor assistant and a Spider expert.