I wish I knew.

[What was that about comforting?]

They're incorporeal for the most part... at least until they want to touch you, and then they kill fast. I've run across a few of them already and the only sure way to get away is to run until you reach a shelter that you can barricade.

[A door slams shut loudly up at the far end of the corridor, and something seems to whisk past them both just out of sight.]