Bill considered the problem of his non-functional time machine for several days. After the first test failed, he had almost completely dismantled the device, searching for mistakes, incorrectly connected wires, flaws in his design, and anything else that could have kept it from working properly. But everything seemed correct.
So he'd put it back together and tested it again. Again there was a flash and a lingering burnt smell, and again he completely failed to float off into the future.
For an hour or so, he'd puttered about with the machine, attempting to figure out if it had done anything at all, eventually concluding that it hadn't. In frustration, he'd gone upstairs to find something to eat.
And there, he discovered another clue.
For several months, Suzanne and Lynda had been talking about painting the kitchen. They both agreed it needed it desperately, though they were unable to see eye to eye on what color it should be. Suzanne favored white, Lynda wanted yellow. And in the last few days, they'd decided to stop talking about it and actually do it. And that very morning, just as Bill had finished making his coffee, they'd barged in with brushes and dropclothes and had started painting the kitchen white.
When Bill wandered upstairs to find a bit of lunch, he was shocked and amazed to find them painting the kitchen yellow.
"I thought you were going to paint this white," Bill asked the girls in astonishment.
Suzanne answered him. "We tossed a coin, and she won."
Forgetting his hunger, Bill ran back downstairs.
He'd been sure that Bert had been eating a sandwich, not a banana, despite the physical evidence to the contrary. Now he found his housemates painting a room yellow when they'd previously been painting it white.
He looked at his machine. Suddenly he understood.
"This isn't a Time Machine," he said, "It's a Time Shifter!"
Through some mistake in his logic, he had made a machine that somehow changed the past. It actually seemed to alter time slightly, to make minor changes in history. It was a machine that "shifted" the recent past, a Time Shifter.
Bill thought about the implications of this. He seemed to have no control over what changed. It seemed to be entirely random. First a sandwich changed to a banana, then a decision about paint color was altered, based entirely upon the way a coin had fallen.
What would change the next time he pushed the button? The changes he'd seen so far had been of no real significance... but what if the next change resulted in someone's death? He also had no idea of how far back in time the Time Shifter could effect changes; perhaps the next time he pushed the button, he'd find himself in a world where the Nazis had won World War II.
Furthermore, only he seemed able to remember the previous incarnation of things. Everyone else was totally unaware of the changes in history. Perhaps being in contact with the Time Shifter somehow had an umbrella effect on him, making him the only person with intact memories of the way things had been before.
He worried greatly about what to do next. Should he destroy the machine now, before something dreadful happened, or instead continue with his experimentation?
