Charles Dickens got it right.
Some hundred and eighty years ago, he wrote a passage in Oliver Twist describing a haunting:
He could trace its shadow in the gloom, supply the smallest item of the outline, and note how stiff and solemn it seemed to stalk along. He could hear its garments rustling in the leaves, and every breath of wind came laden with that last low cry. If he stopped it did the same. If he ran, it followed--not running too: that would have been a relief: but like a corpse endowed with the mere machinery of life, and borne on one slow melancholy wind that never rose or fell.
That sentence-- not running too: that would have been a relief-- is key. The undead are not in a hurry, they are never in a hurry; if they ever for once hurried that would break the tension.