Rush hour, London Tube. We sit down across from each other while a third films. We begin discussing things that will get a conversation going. Kids. Evolution. Whatever.
One begins speaking and gradually pulls out a "TALKER" sign. Once we have passengers' attention the other begins speaking and hands the first a "LISTENER" sign. We switch signs. Other passengers begin listening and butting into the conversation. They receive "TALKER" or "LISTENER" signs depending on their role.
Eventually the immediate section of the train is fully equipped with signs. They are switching signs between themselves and conversing with each other. They are talking and listening.
All video footage from inside the Tube was destroyed.