In Chapter 1, "The Spy," of The Killer Angels, what dangers would the spy encounter while riding at night?

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.

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... 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.

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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.