And yet the absence no longer felt empty.

The dark surface made room for something else. It brought not an image, nothing either sight could identify. No, the blindness brought a feeling. Where perception failed, a sense of pressure emerged; a persistent apprehension of dread.

Though, all of that was in Yves.  
Not in the mirror.            

Yves turned away from the mirror and looked at Midnight.

She was already looking at him. Or rather, she had never stopped.

He knew that she felt his apprehension. Midnight had seen him shift many times before, and she had seen him return, back in the beginning, when everything had been so, so much worse. Yet for all his attempts to explain the experience over the past three years, Yves had never found a way to show her what happened beyond the mirror. He had conjured illusions for her, some intricate, others deliberately abstract, but eventually, every one of them had failed for the same fundamental reason: any representation required him to render the experience into something that could be observed from outside.

did not permit an outside. Yves doubted it could be recognised as space, or substance, or even just absence; not by anything that remained beyond it. There was no external vantage from which to construct a faithful model, no conceptual window through which Midnight might be shown what he perceived there. What he was there. You had to be there, as they said. Quite literally.