Huh. A nice twist on the group improv/story-telling.
The Unknown is a sneak, eh? I wish you'd been able to flesh out that role's motives for speaking with each person first. Maybe Unknown knows everyone in some direct or 2 Degrees of Separation indirect way. I've seen a few movies and Twilight Zone episodes with that character. It plays oddly, but creates "good" drama. There should be a break halfway through or near the climax where one of the players demands to know who the Unknown is and why they get so much say in things. Fun!