A young teacher in a suit walks along a school corridor into a classroom, strips off his jacket and, in shirtsleeves and waistcoat, fills the blackboard with triangles and the Pythagoras formula while lecturing a silent class of teenagers who stare back from their desks. He grows steadily more manic, and in the closing minute he is shot in tight close-up still explaining the lesson while holding a hatchet in one hand; the tape colour in that final section is damaged to a heavy red wash.