A huge, blinking flying object from space emits a glowing ball of electrical energy, which races toward the Earth. It intercepts a man driving on an isolated road in the American Southwest desert late at night. It takes over the man's mind, directing him to LabCentral, a U.S. research facility, where a pair of scientists have been tracking the flying object. The possessed man knocks out a security guard, then proceeds into the main building where the entity leaves the driver and enters the mind of Dr. Hubbell Eliot, the LabCentral chief. Meanwhile, in a research lab below, astrophysicist Dr. Leslie Gaskell and his computer science associate, Dr. Arnold Culver, have been tracking the flying object. They realize that it is not only headed toward Earth but is moving under intelligent guidance. Attempts to destroy with nuclear missiles fail, and the object dives into the Pacific Ocean off the coast of
Mexico. The two scientists, along with Vera Hunter, LabCentral's staff photographer and Gaskell's girlfriend, rush to Mexico. Upon their arrival, they see an enormous glowing dome appear on the ocean horizon. The next morning, on the beach outside their room, they find that a very tall machine has appeared; its four-legged body has two mobile antennae. They use a helicopter to land atop the machine, glimpsing its complex inner workings before being forced to leave and fly back to LabCentral when the machine begins to move. The possessed Dr. Eliot telepathically directs the machine. Now named Kronos by the news media, it methodically attacks power plants in Mexico, draining all their energy. In doing so, Kronos grows larger, consuming more power as it moves from one power source to the next. Four Mexican Air Force fighter planes attack, but the ever-growing alien machine easily destroys them and continues on its rampage. While Kronos is absorbing energy, Eliot is momentarily freed from the influence of the force controlling him. Eliot tells his colleagues that Kronos is an
energy accumulator, sent by an alien race that has exhausted its own natural resources to drain all the Earth's power and then return it to their dying world. On Eliot's recommendation, the
United States Air Force sends a
B-47 bomber to drop an
atomic bomb on Kronos. Gaskell warns the Air Force general in charge that an atomic explosion will simply supply the alien machine with more energy. The general attempts to abort the mission, but Kronos, aware of the plan by way of Dr. Eliot's mind, magnetically draws the jet to crash into it, absorbing the bomb's nuclear blast. The alien machine, now grown to an immense size, appears unstoppable, harvesting all forms of energy at will. In another uncontrolled moment, Dr. Eliot locks himself in an hermetically sealed room, trapping himself and the energy force. As Kronos draws near Los Angeles, Gaskell realizes that reversing the machine's polarity will force it to feed upon itself, until it implodes. Gaskell, Culver, and Vera convince the Air Force to bombard Kronos with nuclear ions, which will cause the polarity to reverse. Kronos is obliterated in the resulting implosion. ==Cast==