The scout, Harrison, was actually a real-life spy for the Confederacy, working under the occasional supervision of Lt. Gen. James Longstreet. Harrison, a Richmond stage actor, had a cover story to use when necessary: He was a "half-witted farmer... terrified of soldiers," whose wife had run off, and he was looking for her. This would, he thought, be a sufficient tale to tell if he was caught alone in the middle of the night.
It was a rough night for Harrison. Pelting rain and constant lightning prevented him from taking refuge under trees. He quoted from Shakespeare during the storm. He took a crossroads just before dark, not knowing if it would lead toward Lee's army or the Union lines. As he crossed South Mountain in the twilight, he had to dismount, since his horse refused to move up the rugged trail. The rain made the hot weather cooler, and he ate his meal in the downpour. Although he now knew he close to the Confederate lines, the night was the most dangerous time for him.
... few men rode out at night on good and honest business, not now, this night, in this invaded country.
Travelling at night did provide him with the cover of darkness, however. When he finally reached a sentry, he worried that he might be shot.
With some you postured and with some you groveled and with some you were imperious. But you could do that only by daylight, when you could see the faces and gauge the reactions.
The sentry was a Confederate, but even then, he knew he was not safe, since if no one knew him, he could be hanged as a spy.