The computer has been closed down and sits in the dark.
The room, like the house, is empty. Some family event sees them all elsewhere. A desk lamp flickers and comes on. The mouse moves slightly. The screen lights. Coloured pixels begin to dance. They gradually align and realign across the screen. Finally, they slow down and come to a halt. They leave a glowing shape of several spaced-out icons, maybe signs, maybe symbols or characters. No one was there to see what may well be a coded message. It may be something that people should know about. It may be important. This unexpected missive could well be a warning that the world should know about!
It sits glowing its communication out into the unlit room for a number of long minutes.
Abruptly the lamp and screen go black. There is no evidence that this had ever happened. Nothing was witnessed.
Whatever it was, it didn’t leave a message…