Matthew, who had once been one of her primary sources of comfort and support, had become merely another obstacle to be navigated.
-- The Narrator from the Perspective of Robin (chapter 4)

Importance: Robin thinks this after the severed leg arrives in the office and she thinks of having to go home and justify her job to Matthew, once again, in light of what has happened. The quote shows that Robin is at a crossroad in her life as Matthew used to meet her needs, but he no longer does. She is outgrowing their relationship.

Strike knew how deeply ingrained was the belief that the evil conceal their dangerous predilections for violence and domination. When they wear them like bangles for all to see, the gullible populace laughs, calls it a pose, or finds it strangely attractive.
-- The Narrator from the Perspective of Strike (chapter 10)

Importance: Strike thinks this as he goes back to where he grew up and thinks of his mother's relationship with Whittaker. The quote is significant...