congregation starts to think of him very differently from the way they did before, and they treat him differently as well.  He becomes a rather terrible presence, despite his gentleness and reputation for goodness. 

Mr. Hooper's first sermon after putting on the veil addressed "secret sin, and those sad mysteries which we hide from our nearest and dearest, and would fain conceal from our own consciousness" if we could.  His congregation feels as though he has "discovered their hoarded iniquity of deed or thought."  Now that they feel vulnerable, they neglect to return Mr. Hooper's greetings in the street or invite him to Sunday dinner as they used to do.  He becomes somewhat of an outcast because he has essentially admitted to everyone that he has a secret sinful nature as well as insinuated that they do as well, and this makes people extremely uncomfortable.  However, he feels that he must continue to wear the veil, likely because it is the only way to attempt to tell the truth about the thing we all try to hide: the fact that we are sinful.  In wearing the veil, he at least admits this truth about himself where everyone else tries to hide it.

In Nathaniel Hawthorne's short story "The Minister's Black Veil," most everyone became terrified of Mr. Hooper the moment he donned the black veil. People trembled in his presence, and children in the streets fled from him. However, sinners whom he converted to Christianity felt drawn to him, and the dying specifically called for him to be at their death beds.

As Hawthorne phrases it, the black veil made him a very "efficient clergyman" in that it had a powerful effect "over souls that were in agony for sin," meaning over people who felt their lives had been torn apart by sin. As Hawthorne explains, sinners who saw him felt that they were "with him behind the black veil," and this perception made them feel like he was bringing light into their lives, meaning spiritual enlightenment into their lives.

Similarly, the sinners who were dying called for Mr. Hooper, refusing to leave this earth until Mr. Hooper had appeared. When he came, they felt comforted by his words of consolation but also shuddered in fear at the sight of the veil because they recognized the similarity between the veil he wore and their own souls.

As Mr. Hooper explains on his own death bed, all human beings hide their faces, their souls behind black veils because all refuse to admit to their sins. Hence, both the sinners seeking redemption and the dying sinners were able to intuitively understand the veil's meaning and to feel a special bond with Mr. Hooper for wearing the veil. The bond was formed due to the fact that, in wearing the veil, Mr. Hooper shows he understands their natures and what they are secretly going through. Yet, despite the bond, they also shrank in terror because sin, as a separation from God, and its consequences are terrifying things, just as absolute darkness is a terrifying thing.

It is widely believed by the local townsfolk that Mr. Hooper committed some sort of secret sin with a young lady who's recently passed away and over whose funeral Mr. Hooper himself presided. It's never actually spelled out, but it would appear that the secret sin in question is some kind of affair.

A couple involved in the young lady's funeral procession engages in a spot of speculation concerning the alleged relationship between Mr. Hooper and the girl he's just buried. One of them reckons that she's just seen the spirit of the young lady walking hand in hand with the minister. This would appear to indicate a belief that the two were a little too close to each other than they ought to have been.

For a man in Hooper's position, a man of God, not to mention an engaged man of God, having an affair would be a very grievous sin indeed. It is further speculated that his overwhelming guilt over this affair is the reason why he goes around wearing a creepy, mysterious-looking black veil.

Mr. Hooper's not telling, of course, and indeed takes the secret with him to the grave, but it's not unreasonable to surmise that he did have an affair and that the black veil is an outward sign of the overwhelming guilt he feels about it.

Elizabeth is Mr. Hooper's fiancée. She is at first less given to ascribing sinister motives to the veil that the Reverend Hooper wears over his face. Eventually, however, she asks him to remove it. When he refuses, she becomes terrified, and to assuage her terror, the Reverend Mr. Hooper tells her that his veil will not persist through eternity. She is the first person to whom he explains the possible dual meaning of the veil, but he refuses, despite her requests, to take it off or to even partially reveal his face to her. She refuses to marry him, which plunges him into great sadness. However, years later when he is on his deathbed, Elizabeth, coincidentally, is his nurse. 

Hooper is presented as an "ordinary" minister.  He is not a fire and brimstone preacher, but instead "strove to win his people heavenward by mild persuasive influence rather than to drive them thither." After he dons the black veil, a simple piece of cloth that covered his face, the people, curious about why he did this since he offered no explanation, begin to speculate.

When the Parson officiates at a funeral, Hawthorne remarks, “A person who watched the interview between the dead and living scrupled not to affirm that, at the instant when the clergyman’s features were disclosed [as he leaned over her and the veil moved] the corpse had slightly shuddered, rustling the shroud."   Of course, with his typical ambiguity, Hawthorne adds, "A superstitious old woman was the only witness of this prodigy."  A pair of townsfolk make a similar remark during the procession to the graveyard after the service.  They "fancy" that they saw " the minister and the maiden's spirit ... walking hand in hand.''  Of course this is not presented as a fact, just as a "fancy."  Such is the power of a simple veil that people are willing to see and believe things of their minister that they never had before.

The positive side of the veil is that it makes Hooper a better minister ... his participation in isolation and guilt, the result of the veil, makes him more understanding of the wounded in his congregation.