In the year 2021, data too sensitive to send over the Internet or store on traditional media is instead stored deep within the brains of specialized data couriers. Johnny Mnemonic (Keanu Reaves) is one such courier, having had a specialized data storage system implanted in his head. During his latest job, Johnny discover that the size of the data package is larger than can safely be stored in his brain, but opts to go ahead and do so anyhow. To make matters worse, the information is stolen from a powerful pharmaceutical corporation, inspiring the company to whom it originally belongs to send assassins after him. On the run from the hired killers, Johnny has limited time to get the data safely downloaded before the overcompressed information kills him. Unfortunately, it can't be downloaded without an encryption key, part of which is missing. Johnny eventually encounters and enlists the help of a gang led by J-Bone (Ice T) to extract the information, and a startling revelation is made about the nature of the data.