The fog around them has been pushed to the side. To Mary, it feels rather as if they're caught in a small room, a room which contains Dickon and Mary and Adam and the fallen lady and half of Mary's tree.

But the room is cold and chill, and anything but comforting; and the walls keep swirling and changing and billowing inwards, as if something is battering to get in -

Something is battering to get in.

Mary grips Dickon's hand tighter, and glowers at Adam, still; he's better than the enemy outside, but that doesn't make him safe.

(And it's better to think about him than about what will happen if the Dark gets in.)