In this hallway, lit only through the distant glass panes of the front entrance, it was dark enough that the corners were hugged with shadow -- but that was normal, a product of the Institute's night-time ambiance.

Or was it?

Streaking from the shadow cast by the angle of the wall, a black cat suddenly wound its purring way around Al's ankles, moving with total self-assurance and no heed whatsoever for his balance.