After winning out over several more experienced composers to score a sci-fi film, he spends a weekend in a cabin trying to develop a song that sounds like a 'universal greeting' based on the producer's instruction.

Finally composing something that he believes is worthwhile, he calls his girlfriend, who is the producer for an internationally syndicated talk radio show, who accidentally broadcasts the song.

The following day, while recovering from a hangover, Devereaux is visited by a Martian who claims that they heard the greeting and have come to Earth to establish lasting peace and prosperity on the planet—only to immediately recant and state that he was joking.

Devereaux tries to shoot him, but discovers that the Martian has the ability to both read minds and teleport, allowing him to predict and dodge any attack.

Around the globe, billions of Martians begin to wreak havoc with their abilities, revealing intimate secrets, appearing and disrupting major sporting events, and voyeuristically spying on couples who are having sex (as they cannot reproduce sexually).