The Castle Inn by Stanley J. Weyman

Mr. Thomasson was mistaken in supposing that it was the jerk, caused by the horses' start, which drew from Julia the scream he heard as the carriage bounded forward and whirled into the night. The girl, indeed, was in no mood to be lightly scared; she had gone through too much. But as, believing herself alone, she sank back on the seat -- at the moment that the horses plunged forward -- her hand, extended to save herself, touched another hand: and the sudden contact in the dark, conveying to her the certainty that she had a companion, with all the possibilities the fact conjured up, more than excused an involuntary cry.

The answer, as she recoiled, expecting the worst, was a sound between a sigh and a grunt; followed by silence. The coachman had got the horses in hand again, and was driving slowly; perhaps he expected to be stopped. She sat as far into her corner as she could, listening and staring, enraged rather than frightened. The lamps shed no light into the interior of the carriage, she had to trust entirely to her ears; and, gradually, while she sat shuddering, awaiting she knew not what, there stole on her senses, mingling with the roll of the wheels, a sound the least expected in the world -- a snore!