John Carpenter's Tales of Science Fiction: Twitch

 August 1977. Astronomers detect the so-called "WOW" signal: a burst of sound from deep space, near the constellation Sagittarius. The signal is believed to be extraterrestrial in origin. The next month, the astronomers send a reply. Boy, is that a huge mistake. Because more than four decades later, the alien intelligence has sent an invasion force of exactly one photon--and it's the kind of microscopic threat we could have never seen coming...

In a desert town one hour north of L.A., Lieutenant Ron Pinkerton watches in horror as law-abiding citizens begin to lose their minds--and the laws of gravity. And then astrophysicist Marisa Stringfellow appears, telling Pinkerton the craziest thing he's ever heard: an alien entity is taking over minds one by one and using their hijacked bodies to create as much mayhem as (in)humanly possible. The tell-tale sign: a violent twitch that means: goodbye, nervous system. And now humanity's last chance lies in the hands of hardboiled cop and a heartbroken scientist... that is, until one of them begins to twitch.