A restricted mood is created from the outset of Chapter 27 when Grace establishes the kind of imprisonment she is enduring, both physically and mentally. At the very opening of this chapter, a happy mood is created through a description of a sunset she witnesses, but immediately this is undercut through the way that she changes her perception of this beautiful sunset, making it much more uniform and ugly. Note how Grace describes the way she chooses to perceive the sunset:
And so this morning I saw only the usual form of light, a light without shape, coming in through the high-up and dirty grey windows, as if cast by no sun and no moon and no lamp or candle. Just a swathe of daylight the same all the way through, like lard.
The rather depressing simile at the end of this quote, where the daylight is compared to such a common and perhaps repulsive object reinforces the rather depressed mood that restricts Grace's character and shows how her status as accused and prisoner impacts upon the way that she perceives the world around her. The quote also establishes the dirt and grime of her setting in prison, referencing the "dirty grey windows" and how through them only "light without shape" can enter, stripping nature of its beauty and distinguishing qualities. This description helps establish the mood of these chapters as it reveals a lot about Grace's external world compared to her rich, internal psychological existence.