The wonder, the miracle, the glory of ubiquitous computing was that nobody ever had to buy another electronic device again. All that was needed was an interface - a pocket modem for some, a neurological implant for others - to hook into and share whatever ambient memory was nearby.

Ambient memory there was in plenty. Every toaster, lamp, and refrigerator had more memory than it knew what to do with, as much as any Cray supercomputer ever had. Memory was built into clothing, countertops, and rugs. Government trucks with fogging devices sprayed nanochips small as dust-motes down every commercial route in the world, from whence they shifted into every home, school, or tract of wilderness in existence. Once the protocols for sharing data were worked out, no matter where you were, you had access to all the computing power you might ever need.

All the world was transformed into a single smart system.

Briefly, the economy boomed. Banks and factories, fashion design firms, feed companies, county planning agencies . . . everything ran off of free and plentiful computation.

It was inevitable there should be a few cross-links.

Perhaps it was the Vatican cross-linking with a planned armored-car robbery and a child's wondering why evil existed. It may have been a weather satellite short-circuiting a tuna cannery, a wood-milling device, and a Japanese translation engine. It could have been any ten million programs combining badly with any thirty million others. Whatever caused it, there was a fatal error. Swift as thought, across the globe, into every device and every wired brain the words flashed: THIS SYSTEM HAS PERFORMED AN ILLEGAL OPERATION AND WILL NOW SHUT DOWN. PLEASE RELOAD AND REBOOT.

Then the system crashed.

History records, in letters painfully scratched upon parchment with a quill pen, that the very first words of the Second Dark Ages were, "Did anybody think to make a backup?"