The monitor showed a jet black hole almost completely erasing the factory district. It was well outside the realm of what he could pass off as land subsidence. Even if he took “emergency measures” to erase the entire city of Snowfield, that hole alone would certainly remain for all of America to see.
In addition, a surveillance satellite would pass high above the city in a few more minutes.
It was a civilian satellite, supplying data to civilian researchers in close to real time. The day it showed a hole of this size this clearly, the concealment of Mystery would be the least of his worries.
He was just about to phone Francesca to inquire how she intended to take responsibility, when another abnormality began on the monitor. No sooner was the colossal hole filled in than, almost like time was rewinding, the toppled smokestacks and crumbled walls of the factories began to reform. Even the burnt grass in the empty lots regained its verdant life.
“...What is this...?”
A transmission from Francesca reached the bewildered Faldeus.
“Yoo-hoo? Are you surprised? I bet I softened that grumpy look of yours a little. Well?”
“...This is no laughing matter. What exactly did you do?”
“Oh, just an illusion,” Francesca roared with laughter as she answered Faldeus’ question. “Of course, it’s my Noble Phantasm as a Heroic Spirit, so it can do things orders of magnitude more stunning than turning a wasteland into a snowy mountain! Oh, I almost forgot — I can’t say why, but the people who were brawling down there seem to have suddenly reached a peaceful settlement. Mysterious, isn’t it? Maybe it was the power of love? Isn’t that lovely? Love, I mean!”
Faldeus ignored the better part of her words and correctly deduced that she must have struck some kind of deal. Before he could press her about it, however, Francesca gave him a reminder by way of a warning.
“Don’t forget — until it’s all over, we’re enemies in the Holy Grail War too.” Then, almost incidentally, she said something about the restored factories that Faldeus found difficult to believe.
“They may look like they’re back to normal, but it is still an illusion, you know? You can touch them, live in them, even go on using them as factories and workshops, but that’s all they are! In about five days the world will realize it’s being fooled and they’ll crumble just like they were, so take care of the cover up before then!”

Fate/Strange Fake: Volume 4, Chapter 12 ("Day 2, Morning")