Johnny Mnemonic is a short story by William Gibson, and a movie loosely based on the short story. For the movie, see Johnny Mnemonic (movie).
The short story appeared in a collection of short stories by Gibson, called Burning Chrome. It takes place in the world of Gibson's cyberpunk novels, predating them by some years, and introducing the character Molly, who plays a prominent part in the novels.
Johnny is a data trafficker. He has undergone surgery to have a data storage system implanted in his head, which he is unable to access. He makes a modest living in the Sprawl by physically transporting sensitive information for corporations or individuals. The underlying idea is that there is some information so sensitive that it is safer to send it by human courier than over computer networks (which are vulnerable to hackers).
As the story opens Johnny is in trouble because the data stored in his brain was originally stolen from the Yakuza (Japanese mafia), and they send out a contract killer to take care of Johnny. Forced to flee, Johnny meets up with Molly, a "Razorgirl" who has undergone extensive body modifications, most notably fingernail blades. Together they plan to retrieve the data stored inside Johnny, and enlist the help of a retired navy dolphin, and a gang of anti-technology misfits who live high in the Buckyball domes covering the Sprawl.
At the end of the short story Johnny and Molly intend to make a living for themselves by retrieving all previously stored data in Johnny, and blackmail his former customers with it, living with the anti-tech gang. The Sprawl setting and Molly later appear in Neuromancer, where it is implied the Yakuza eventually caught up with Johnny and killed him.
