The theme of good and evil battling is carried through in Chapter 9, "The Leech," a ponderous and philosophical chapter with little action and much positioning of characters. We see the double meaning of the word "leech," the decline of Dimmesdale under his weight of guilt, the development of his relationship with Chillingworth, and the point of view of the townspeople, which have strikingly opposing opinions about the influence of Chillingworth on the minister. As he ingratiates himself with the young minister, and the town sees Chillingworth as "a brilliant acquisition." On the other hand, they suspect that the relationship and proximity of Chillingworth and Dimmesdale have led to Dimmesdale's deterioration.
Hawthorne purposely uses the old-fashioned term "leech" for "physician" because of its obvious double meaning. As a doctor, Chillingworth seems to be making complicated medicines that he learned at the feet of the Indians; he also appears to be sucking the life out of Dimmesdale.
