The story is set in a dystopian future where overpopulation has led to a strict one-child policy. Seven identical sisters, each named for a day of the week, have to hide their existence. When Monday goes missing, the others must figure out what happened and stay hidden.
The story of What Happened to Monday is set in a future with limited resources and one-child policies. The sisters, named after the days of the week, try to live secretly. But when one goes missing, chaos ensues and their lives are in danger.
What Happened to Monday is not based on a true story. It's a work of fiction that takes us into a made-up world with its own set of rules and circumstances.
Since I don't know the specific short story, it's difficult to say exactly what happened on that Monday. It might be that the main character received some unexpected news that set the plot in motion. Maybe it was related to a relationship, like a letter from an old friend or a breakup. Or perhaps it was something to do with a mystery, like a strange object being found.