The set turns out to be an art gallery with paintings on the walls and centre stage an empty plinth. A janitor wanders on stage sweeping. When he reaches the plinth he props up his broom, pulls an apple out of his dustcoat pocket and rubs it absentmindedly on his lapel. Resting the apple on the plinth he picks up the broom again and continues sweeping (exit stage right). A group of art enthusiasts enter and seeing the apple on the plinth begin what to Billy is probably a familiar critique. Eventually the janitor returns, grabs his apple and munches into it as he departs. Cue general critical confusion and recanting.
After the play the tutor Mark Clare approaches Billy who he recognises. As they talk Billy becomes aware of something behind him. It's a line of kids each holding a copy of the poster for the play. They want Billy to sign them, which he does. The circle completed they all go home.
Image: A signed poster. (Thanks M, thanks B)