You wake up with a start; you hadn't even known you dozed off.
You look around, and see that the subway car you're on has stopped in the tunnel. There are some other passengers, and they seem to be dozing off as well. Must be stale air. You try to peer out the door of the subway car to see where you've stopped, but it's too dark. The lights flicker. For a moment, the "Emergency Exit" sign above the window seems to read just "Emerge".
You realize you don't know where you're going.
You then realize you don't know where you got on.
Or how you got on the subway.
But there is one thing you're certain of.
You know who you are.