In Chapter 12 of The Scarlet Letter, Chillingworth appears at the scaffold at the same time as the appearance of the meteor. Why?
There are three scenes in the novel which take place at the scaffold, and Chillingworth is present in each one. Chapter 12 recounts the events of the second time the characters visit the scaffold. Dimmesdale climbs the steps alone, seeking relief from his terrible guilt; there is no relief for him, however, because his act of contrition is hidden by the dark night and no one hears his tormented cries. When Pearl and Hester happen upon him, Pearl asks if he will stand with her and her mother in the light of day. He will not.
The appearance of the meteor, the fantastic red light in the sky, interrupts the scene in a mysterious way. It does not, in fact, take the definite shape of the letter A. It is Dimmesdale who sees it as such. The narrator notes that a man with a different sin might have observed it differently. Nevertheless, it is in this weird and unnatural light that Chillingworth enters the scene, his features distorted in the illumination. Dimmesdale is repulsed by him, demands to know who he is, and tells Hester that he hates him. Chillingworth skillfully convinces Dimmesdale to come down from the scaffold and leads him home. His seemingly solicitous manner hides his real purpose: to keep the minister from a public confession so that Chillingworth can continue his revenge. So long as Dimmesdale bears his guilt, he will continue to live in torment.
The dramatic composition of the scene works symbolically to develop the novel's major theme. Dimmesdale's "scarlet letter" in the sky symbolizes his deeply felt guilt, the scaffold symbolizes confession and freedom from his guilt, and when Dimmesdale reaches what seems to be a moment of supernatural revelation when he might well make his confession public, Chillingworth's entrance "breaks the spell," and Dimmesdale reverts to his own weak nature:
With a chill despondency, like one awakening, all nerveless, from an ugly dream, he yielded himself to the physician, and was led away.
Chillingworth appears at the exact moment when Dimmesdale, transfixed by his vision of the fiery scarlet letter above him, might well have escaped him.