The HIDTV software decoded one last, perfect ghost: the sound of his own heartbeat, from thirty seconds in the future, thudding loud and fast just before the door swung open.

For three weeks, Elias became a ghost hunter. He watched the premiere of a Star Wars sequel filmed in 1989. He listened to a radio broadcast of the Hindenburg landing safely in New Jersey. He saw a presidential debate where the third-party candidate won.

Elias didn't know what "ghosts" meant. But he soon found out.

He looked at the USB stick. If he pulled it out, the software would crash. The ghosts would vanish. The door would stop creaking. But the broadcast of his own terrified face would stop, too. And whoever—or whatever —had been watching from the other side of that future window would lose its signal.

The text at the bottom of the HIDTV interface changed one last time.