The story takes place in the jungle coast of Venezuela at the end of World War II. Murphy (Peter O'Toole), an airplane mechanic, is the lone survivor of a German submarine attack on an armed merchant ship. Murphy wants to get even. A missionary nurse (Sian Phillips) helps him recover from his injuries, a dying pilot tells him of a repairable airplane, and a French engineer helps him develop some makeshift bombs. With their help he restores the airplane so as to wage his own private war on the submarine. Though he has never flown a plane before, he goes in search of the German boat to harass it with homemade bombs. In the process, he is always on the brink of disaster because of his erratic flying. Though his daredevil efforts seem to have little effect, he keeps on trying.