Without being aware that he does this action, the Reverend Arthur Dimmesdale places his hand upon his heart.
When Hester's husband returns to find his wife, he is shocked to find her on "the pedestal of infamy." Later, he visits her in prison and asks her who the man is who has wronged them both; when Hester refuses to reveal his name, the husband vows to find this man.
Calling himself Roger Chillingworth and fashioning himself as a physician because he possesses knowledge of science and herbs, Chillingworth ingratiates himself to the Reverend Dimmesdale, whose health has been failing. He attends the minister and then moves into his home in order to be constantly available.
In Chapter X the physician and his patient, who does not recognize his enemy, discuss guilt and sin. The minister contends that some people hide their sins so that they can continue to serve the better interests of men. Chillingworth argues that such men deceive themselves because their guilt will "propagate a hellish breed within them." Dimmesdale concurs,
"...it must needs be better for the sufferer to be free to show his pain, as this poor woman Hester is, than to cover it up in his heart."
Hearing the minister, Chillingworth suggests that the Reverend open his heart to him. But, the minister adamantly refuses, and he rushes from the room. Later, he apologizes to the physician with remorseful words and entreats the physician to continue his care for him. Then, one day the minister falls into a deep sleep in his chair. Chillingworth advances toward the minister; he places his hand upon the minister's chest and pushes aside his clothing.
But what a wild look of wonder, joy, and honor! With what a ghastly rapture...he threw up his arms towards the ceiling, and stamped his foot upon the floor!
Chillingworth now understands why the minister holds his heart so often. Finally, in Chapter XXIII, as he stands on the scaffold with Hester and little Pearl, Arthur Dimmesdale pulls aside his clothing, showing his chest to the crowd and revealing the A upon his own chest.
Dimmesdale's gesture, which is described as having "grown involuntary with him" in Chapter 17, is to clutch at his heart with his hand, or at least to hold his hand against his heart. This clearly suggests the guilt that Dimmesdale carries with him, a guilt which is not released until he confesses at the end of the book. Many of the witnesses to the confession, Hawthorne tells the reader, claim that they saw the letter "A" imprinted in the flesh over Dimmesdale's heart when he confessed. There are a number of theories as to why this could have been so, but clearly the image, as well as Dimmesdale's gesture, indicate a heartsick man.