Another Me?

I don't know how they know me
They simply do.
It's as if they've seen me before
Yet they wonder where.
Who is this other me?
When all worlds vanish into darkness
And I am left alone with them
Who is left to be with me?
Who, left behind, will know me?
All think they know me
They've seen me before...
This supposed double of mine.
Think they will ever know it is actually me?