After the duel, Barnabas goes and knells down next to Jeremiah. As his knee hits the grass you can see that the grass is a square piece of cloth since it moves slightly forward. it is at the bottom of the screen when it happens. (Note: Whenever grass is seen on the set, it consists of a loose thin green carpet thrown across the stage floor. It often moves under the actors' feet and occasionally you can see where the carpet ends, revealing the stage floor).