In 1954, a calm desert morning turns into a chilling investigation when two New Mexico State Police officers come upon a little girl wandering in a catatonic state near Alamogordo, closely followed by a ravaged travel trailer and a dead, mutilated owner in the nearby cellar. The scene is grim and puzzling: no money has been taken, yet violence and ruin are everywhere. As the officers process the sites, they notice a pulsing, ominous sound outside, and one of them, left alone to wait for backup, fires his weapon in a desperate moment of terror.
An FBI agent arrives to help piece together the mystery. He sends a sample of a trench coat-like cast from the trailer’s vicinity to Washington, D.C., only to be met with an unusual response: Drs. Harold and Pat Medford—a father-and-daughter duo renowned for their work with ants—are dispatched by the Department of Agriculture. On a hunch, Harold tests the little girl with the scent of formic acid, a chemical signature of ants. The effect is dramatic: the girl breaks from her catatonia in a scream of fear, crying, “Them! Them!”
The investigators, accompanied by the Medfords, re-trace the crime scene. During the search, Pat is charged by a giant foraging ant, and Harold directs the team to shoot off the creature’s antennae to blind it, while a Thompson submachine gun finishes the strike. Harold theorizes that radiation from the first atomic bomb tests near Alamogordo has mutated the ants, driving them to carnivory due to the desert’s sparse food supply.
A helicopter sweep of the desert uncovers a massive ant nest, ringed with human remains. Cyanide gas bombs are deployed, and the trio presses inward. They meet a pair of surviving guard ants, eliminated with a flamethrower and the trusty Thompson. At the lowest levels, they discover evidence that two queen ants have hatched and flown away. Harold cautions that if the queens establish new colonies, humanity could lose its position as the top species within a year.
To keep the threat under wraps and prevent widespread panic, the operation widens in secrecy. Graham and Pat travel to Brownsville, Texas, to question a ranch foreman who was committed to a mental hospital after claiming he’d been forced down by UFOs shaped like giant ants. The hunt continues as one ant queen boards a freighter in Acapulco; its offspring surface in the Pacific and terrorize the crew, with the Navy sinking the ship after two sailors survive.
A report about a stolen sugar shipment leads investigators to a Los Angeles hospital, where a chronic alcoholic swears he has seen giant ants in the city’s storm drains. Tracing a man whose mutilated body was found in the area uncovers another giant ant print, and the team becomes convinced that the final missing queen—and the two missing young sons—are somewhere within the sprawling, subterranean tunnels beneath the city, an underground world spanning more than 700 miles.
Martial law grips Los Angeles, and a curfew is imposed as the search intensifies through the drain network. Peterson locates the two boys, trapped by the advancing insects, and, with a last-ditch surge of reinforcements, pulls them to safety. Graham arrives just in time to confront the ominous queen and her hatchlings, and the Medfords verify that no new queens have escaped. The order is given to destroy the nest, ending the immediate threat but leaving a haunting question in the air: what havoc might follow the other nuclear explosions of the era? Harold answers with a grim, forward-looking honesty: mankind has entered a new world, and no one can predict what we will find.
> Them! Them!
