At the end of the book Susan has been half-vamped by the Red Court and has to constantly resist the urge to drink blood, so she leaves town. She sends Harry a card with exactly three words on it. Awwww...
When Harry was looking at the barbed-wire curse thing and describing it in all it's horrific glory, and then Murphy comes into the room, and Dresden sees her with the Sight. What does he see? An angel with a flaming sword.
I smiled, remembering the vision, sharp and brilliant in my mind’s eye. Murphy, the guardian angel, coming through the door in a blaze of wrath. It was a picture I wouldn’t mind keeping with me. Sometimes you get lucky.
Here's the description:
The door burst open. Murphy came through it, her eyes living flames of azure blue, her hair a golden coronet around her. She held a blazing sword in her hand and she shone so bright and beautiful and terrifying in her anger that it was hard to see. The Sight, I realized, dimly. I was seeing her for who she was.
Harry literally using The Power of Friendship to contact and comfort Murphy while she's in a Nightmare-induced coma. Small, but sweet.