Visitor with Failing Eyesight

My apologies, I'm unprepared.
Let me help you down the hall.
I've been out all day sketching -
well, sort of searching. There was a wave,
a whole dispersal
along the thoroughfare. Like a displacement:
you could SEE it.
I didn't, this time.
Oh yes, let her lie there,
that rug is old.
I'll be out again tomorrow.
There's something else I can't describe -
I'm so sorry, you'd have to see it.
The pink-grey mass growing bigger:
it comes from there.
What an embarrassment, I can't apologise enough.
It wouldn't, anyway,
help you if you saw it.