MacGyver comes along on a expedition to Brazil with his friend, entomologist Dr. Alden. They meet with a landowner and recluse, Trumbo, who is initially hostile. However, when they realize that a mile-wide column of army ants is moving through the jungle, they team together to mount a defense.

MacGyver becomes infatuated with a woman while conducting environmental-impact studies. However, what MacGyver does not know is that the woman was hired to "persuade" him to skip the studies—and if necessary, kill him.