Young Goodman Brown's errand is actually to go where he ends up going, which is to a wild devil-worshiping orgy in the forest. He doesn't tell his wife where he is going because he wants her to think that he will be going on a business trip. The big surprise in the story is his discovery that his sweet, innocent little wife is not only attending the orgy but has an important role in the proceedings. She might have decided to stay at home if she had suspected that her young model-husband would turn up there that night. Young Goodman Brown probably could have made up a fictitious errand and a fictitious destination, but somehow it doesn't seem that the story requires this kind of dissembling. In Hawthorne's excellent story "Wakefield," included in his Twice-Told Tales, the husband leaves home on a "business trip" and doesn't return for a great many years.