'Dark' in the Bible

Woe (judgment is coming) to those who [try to] deeply hide their plans from the Lord,Whose deeds are done in a dark place,And who say, “Who sees us?” or “Who knows us?”

We grope for a wall like the blind,We grope like those who have no eyes.We stumble at midday as in the twilight;Among those who are healthy we are like dead men.