White Noise

“There is another city right under our city and it comes up only when you and I are together. Only you and I know about it and only you and I get to experience it. It keeps itself hidden from the rest of the world. And that is where I live” he said.
“And what happens when you are not with me?” she asked
“I evaporate.” he smiled.
What starts off as a playful liaison for him ends up becoming toxic for her. This thing that they have between them is not normal to say the very least but she is too afraid to question it.
And suddenly a few secrets come to light.
Why does he disappear again and again? Where does he go? Why is he pushing her towards insanity?
And most importantly, was it really chance that brought them together? Or is there a bigger motive to all of this?