The topmost line is the darkness itself, and the classic disposes of it in a single movement. Legge's translation gives a case in which there is no brightness but only obscurity, and says the subject had at first ascended to the top of the sky and will hereafter go into the earth. Everything else in the hexagram describes people managing under a darkening. This line describes the thing doing the darkening, and it describes it entirely as a trajectory.
The figure puts earth above fire, so the highest place in it is the deepest point of the obscurity, and a stroke at the top of the upper trigram Kun stands as far from the light of the lower trigram as the hexagram allows. It is yielding in an even place, correct by the ordinary rule, which is one of the sharper ironies in the classic. Correct placement confers nothing at this station. The line falls not because it is badly seated but because it has nowhere further up to go.
The two halves of the movement are the point. A darkness of this kind does not begin as darkness. It begins as something that rose, and the height it reached is what makes the descent complete rather than partial. The classic passes no sentence, names no punishment and supplies no agent of the fall. It states the arc and leaves it there, with the fifth line, which had to live beside this one, holding the only firmness anywhere in the upper half of the figure.