They didn’t like to think there were guilty people still happily going about their business, sitting in their gardens, doing a sudoku, knowing they had got away with murder.
-- Narrator - Joyce (Chapter 4)

Importance: Joyce describes in her diary why Penny and Elizabeth started the Thursday Murder Club. She explains they looked through Penny’s old cases that had never been solved in hopes they could find new clues to identify the murderer.

Bogdan isn’t Ian’s biggest worry today. If he ends up having to pay him, then so be it. Ian’s biggest worry is being killed by Tony Curran.
-- Narrator (Chapter 5)

Importance: Osman suggests that perhaps Ian will be killed by Tony. Instead, it is Tony who is murdered. Ironically, Ian is the prime suspect.

Three friends, drinking beer, at a table covered with money. Why leave the photo by the body? A warning from Bobby Tanner or Jason Ritchie? A warning to...
-- Narrator (Chapter 17)