Cora wants to argue, not because she’s particularly loyal to the police, but because she wants this to not be her problem. The police never found Delilah’s killer, after all, so there’s only so much faith she can give them. She wants to believe in a world where the police always catch the bad guys, where they get thrown in jail for the rest of their lives, where the survivors can mourn and move on and learn to be happy again. But only children can believe in that world.
