Cold, Dark, and the Color of Red

This is definitely it, "the shimmer" as Tony called it.

It was a calling card. One that was only left when someone wanted Him. How people got this information, Tony never knew, and did not care about. How and why were questions he had stopped asking when the darkness came, no point in asking questions when no one was giving any answers.

The real question wasnt why someone had put out a shimmer, the real question was who?

There may be answers on the street, but there was a window, no curtain, no light, nothing, not even light from another part of the apartment. Likely nothing to worry about, although often things out of place like that were a good place to start...