What does the young Goodman Brown experience in the forest primeval in "Young Goodman Brown"?

In the forest
primeval,suffers a fall from innocence that is not unlike that of Adam.

When
Brown ventures into the forest in order to test his faith, he loses this faith after witnessing
the black mass and seeing his wife Faith there. As the pink ribbons of his once innocent wife
"flutter lightly down through the air," Goodman cries, "My Faith is gone!"
and he learns the terrible significance of this loss.

Goodman Brown
experiences such a dramatic change in his character because he is initially so confident in his
faith. But, this faith is challenged as one by one the seemingly saintly members of his
community demonstrate that they are in league with the devil. For instance, when Brown happens
upon Goody Cloyse, who has taught him his catechism and who he recognizes as "a very pious
and exemplary dame," he is surprised to see her in the forest. Then, he is shocked when
this "pious old lady" notices the traveler "put forth his staff and touch her
withered neck with what seemed the serpent's tongue" and she cries out, "The
devil!....Ah, forsooth, and is it your worship indeed?" Furthermore, she laughs and engages
in conversation with this traveler who has ironically assumed the form of Brown's
grandfather. 
Later, when Brown sees Deacon Gookin and Goodman Brown, he

...caught hold of a tree for support, being ready to sink down on
the ground, faint and overburdened with the heavy sickness of his heart. He looked up to the
sky, doubting whether there really was a heaven above him.

Of course, the most spiritually devastating sight for Brown is that of his wife Faith
"trembling before that unhallowed altar" at the black mass in the forest. He calls to
her, "Faith! Faith!...look up to heaven and resist the wicked one."
At this
point Goodman Brown loses consciousness. When he does awaken, it is as a changed man. For,
having confronted the universal nature of sinful man in the forest, Goodman Brown becomes
cynical and misanthropic. Henceforth, "misery unutterable" pursues him as he has
completely loss his religious faith and his belief in the goodness of humanity.