This line is from Chapter XI of "The Scarlet Letter." In the previous chapter, Chillingworth proposes to Dimmesdale that in order to heal the minister, he must know of all ailments of body and of spirit. To this Dimmesdale reacts with great passion and frantic gestures, crying out that he will not reveal to an earthy physician what ails his spirit. After the minister leaves the room, Chillingworth mutters to himself, "A rare case...I must needs look deeper into it! A strange sympathy betwixt body and soul! Were it only for art's sake, I must search this matter to the bottom!"
While Dimmesdale is asleep, Chillingworth enters with no fear of his waking. (He must have drugged the minister.) He pulls open the vestment of the minister and makes a startling discovery, reacting with a wild look of wonder and horror. And, had a man seen him at that moment, Hawthorne writes, he would know how Satan behaves when he has won a soul. Yet, C. differs from Satan in his look of wonder.
So, Chillingworth works to gain insight into the heart of Dimmesdale and to give more significance to his statement in Chapter IV: "He must needs be mine!" Dimmesdale becomes a victim to "the machinations of Chillingworth"; the physician no longer is so interested in healing his patient; now he wishes to get the minister to reveal what tortures his soul.