The inventor was frustrated. He had spent years, decades, creating a time machine (which was about the size of a shoebox), but now that it was finished, no one would believe him. When he tried to explain his theories to others, they would always respond by saying that if he had really invented a time machine, it would be possible to create a paradox by, say, going back in time and killing one’s grandfather before he had any children. Since this was ridiculous, he couldn’t have invented a time machine.
So the inventor decided to conduct an experiment: he would travel five years into the past and kill himself -- his self from five years ago, that is. This would prove that travel into the past only allowed observation, and so such paradoxes could not arise.
He went out into the hallway outside his office, turned the number dial on the time machine to "5", the units dial all the way up to "year", the directional switch to "past", and activated it. Not much changed, but he hadn’t expected it to; he had always relished continuity (which made it a little unusual that he, of all people, would invent a time machine), and so his furnishings had remained almost entirely unchanged over the thirty-plus years that he’d been living in this house. He expected to find himself at work in his office, and so walked over to it. The door was open a crack, and he was able to look in and see that, yes, he was indeed sitting at his desk, looking at something. He raised the pistol, pushed the door open, and before his old self could react to the sound of the creaky hinges, he shot himself in the head. His old self.
He paused for a moment to see if he noticed any differences: did he have any new memories? Did he still exist? Would one notice if one stopped existing? At this last thought, he chuckled, stepped into the room, and then pushed the return button on the time machine. Apart from the disappearance of his body -- his old body -- and the door closing most of the way behind him, nothing changed. After pausing again to see if he noticed any differences (he didn’t), he went over to his desk to record the results of his experiment. He looked at the time machine and called up the exact coordinates it had recorded, and began writing them down.
But something was wrong. As he finished writing the coordinates, he looked back at the time machine to see what it was. The first thing he noticed was that, although he had pushed the directional switch down for "past", the switch was sticky and it hadn't clicked over. The second thing he noticed was that, while he had turned the category dial all the way up to "year", he accidentally pushed it too far, so it went beyond it, resetting to the smallest unit.
He hadn't set the time machine for five years in the past. He had set it for five minutes in the future.
And behind him, the door hinges creaked.