it creeps in

I don't know when it began or how it even started. 

 Perhaps I left the window open, or maybe I just opened up the door for it. 

Nonetheless it's in the house

 and no matter how hard I sweep and clean it hasn't gone away.

Maybe I’ve waited till it got to the point that now I'm no longer able to clean it even if it appears that I did. 

 Even away from home, sometimes it's on my shoes, even on my clothes. 

It seeped so deep into the crevasse and I’m not sure I’ll ever be able to wash it clean.