p. 24:

They came to the door with me and stood side by side in a cheerful square of light.

A minor example of good writing, an evocative turn of phrase.  But given all that’s gone on during the evening, the classic picture of the host couple bidding farewell to their departing guest almost insists on a sinister subtext.  That square of light, framing Daisy and Tom, shows their outline without shedding any illumination on their turmoil.