What am I?

~ one part short story ~

I do not breathe, and yet I live.
When in light, no shadow do I give.
Though I am behind you, my reflection you cannot see.
And despite your desires, it is futile to flee.
What am I?

The dark caves along the cliffside path would provide good shelter from the rain. Naturally, that was the only thing going through Jasmine's boyfriend's head when he dragged her and his sister inside after the heavens opened on them.

The trio may be dry, but are they safe? The caves may not be as empty as they thought...