What do you think Chillingworth sees when he secretly enters the minister's room? What effect does this incident have on the physician?

Chillingworth arrives in Salem and no one knows who he
really is except Hester, whom he swears to secrecy. He sets out to befriend Dimmesdale
because he suspects that he is Pearl's father. Chillingworth is a physician, and
Dimmesdale becomes his patient. The doctor does all he can to befriend Dimmesdale and
treat him, and they have long conversations about the nature of sin, hidden sin, etc. In
chapters 9 and 10, Hawthorne develops the relationship between these two men. In chapter
10, Dimmesdale falls asleep, and Chillingworth sneaks up on him and pushes aside his
garment to look at the minister's chest. What he sees throws him into an evil
ecstasy:

Had
a man seen old Roger Chillingworth, at that moment of his ecstasy, he would have had no
need to ask how Satan comports himself, when a precious human soul is lost to heaven,
and won into his kingdom.

The
reader never finds out what this is, but from this point on in the novel, Chillingworth
is convinced that what he has seen is proof that Dimmesdale has been Hester's lover and
the father of Pearl. The reader must infer that there must have been some sort of symbol
on Dimmesdale's chest - perhaps a letter A was burned into his chest, or the hairs on
his chest formed the letter A. Or, perhaps he was wearing something around his neck - a
lock of Hester's hair, or a lock of Pearl's hair.

What do
you think?