How does this passage characterize Roger Chillingworth: "He became, thenceforth, not a spectator only, but a chief actor, in the poor minister's interior world. He could play upon him as he chose."
Chapter XI of The Scarlet Letter by Nathaniel Hawthorne
With the clear intention of discovering with whom Hester, his wife, has consorted, Roger Chillingworth has become the physician to the ailing Reverend Arthur Dimmesdale. In Chapter X, Chillingworth enters into a discussion with the minister about why someone would not confess his sins. The Puritan minister answers that some people dare not reveal their sins because if they do reveal themselves "black and filthy in the view of men," they can no longer achieve any good. To this statement, the physician retorts that these men deceive themselves.
When the minister seeks to change the subject by asking if the physician has profited from caring for him, Pearl throws a burr at Dimmesdale through the open window and runs away shouting to her mother to flee because the Black Man has "got hold of the minister...." Her action, of course, foreshadows those of the physician, the Black Man who violates the secrets of the human heart. For, at the end of the chapter, Chillingworth pulls back the vestment of Dimmesdale and takes Satanic delight in what he sees revealed.
This revelation changes unalterably the relationship of the physician and his patient. Henceforth, Chillingworth becomes the fiend that holds the secrets of Dimmesdale's soul, and he can manipulate and torture the minister; he is a "chief actor in the poor minister's interior world." Further in Chapter XI, Hawthorne writes,
...the intercourse between the clergyman and the physician, though externally the same, was really of another character than it had previously been. The intellect of Roger Chillingworth had now a sufficiently plain path before it.....Calm, gentle, passionless, as he appeared, there was yet, we fear, a quiet depth of malice, hitherto latent, but active now, in this unfortunate old man, which led him to imagine a more intimate revenge than any mortal had ever wreaked upon an enemy.
As he has previously told Hester in Chapter IV, "he will be mine," the physician makes plans for torturing the minister and avenging himself as the cuckolded husband upon Dimmesdale. Thus, Chillingworth becomes Dimmesdale's most deadly enemy, the "chief actor in the poor minister's interior world" where he can plant torture. Ironically, the ugly weeds to which Chillingworth alludes as having grown out of a dead man's heart in a graveyard are symbolic of those weeds of revenge that now grow in the black heart of the fiendish Roger Chillingworth.