Well, I think everyone already knows my theory that there is a strong link between Murphy and Mab, going so far as equating the two in some
past,present,future, alternate reality. So here it goes.
First off, I think Harry's accident was to get Murphy involved in assisting Harry in the search for black magic, aka Molly's black magic.
Second, it was Murphy that tipped Harry off to use Charity's blood to divine the whereabouts of Molly.
To be continuted with supporting text and further arguments.
Then he brought everyone a cup of tea, and faded immediately back to the kitchen alcove again while Charity prayed.
Maybe ten minutes later, Murphy knocked at the door and then opened it.
Besides Thomas, she was the only person I’d entrusted with an amulet that would let her through my wards without harm. She wore one of her usual work outfits: black jacket, white shirt, dark pants, comfortable shoes. Grey predawn light backlit her. She took a look around the place, frowning, before she shut the door. “What’s happened?”
I brought her up to speed, finishing with my failure to locate the girl’s trail.
“So you’re trying to find Molly?” Murphy asked. “With a spell?”
“Yeah,” I said.
“I thought that was pretty routine for you,” Murphy said. “I mean, I can think of four or five times at least you’ve done that.”
I shook my head. “That’s tracking down where something is. I’m looking for where Molly’s been. It’s a different bag of snakes.”
“Why?” Murphy asked. “Why not go straight to her?”
“Because the fetches have taken her back home with them,” I said. “She’s in the Nevernever. I can’t zero in on her there. The best I can do is to try to find where they crossed over, follow them across, and use a regular tracking spell once I’m through.”
“Oh.” She frowned and walked over to me. “And for that you need her hair?”
“Yeah,” I said. “Which we don’t have. So we’re stuck.”
She chewed on her lip. “Couldn’t you use something else?”
“Nail clippings,” I said. “Or blood, if it was fresh enough.”
“Uh-huh,” Murphy said. She nodded at Charity. “What about her blood?”
“What?” I said.
“She’s the girl’s mother,” Murphy said. “Blood of her blood. Wouldn’t that work?”
“No,” I said.
“Oh,” Murphy said. “Why not?”
“Because…” I frowned. “Uh…” I looked up at Charity for a moment.
Actually, there was a magical connection between parents and children. A strong one. My mother had worked a spell linked to Thomas and me that would confirm to us that we were brothers. The connection had been established, even though she had been the only common parent between us.
The blood connection was the deepest known to magic. “It might work,” I said quietly. I thought about it some more and breathed, “Stars and stones, not just work. Actually, for this spell, it might work better.”
Charity said nothing, but her eyes glowed with that steady, unmovable strength. I thought to myself, That’s what faith looks like.
I nodded my head to her in a bow of acknowledgment.
Then I turned to Murphy and gave her a jubilant kiss on the mouth.
Murphy blinked in total surprise.
“Yes!” I whooped, laughing. “Murphy, you rock! Go team Dresden!”
“Hey, I’m the one who rocks,” she said. “Go team Murphy.”
Thomas snorted. Even Charity had a small smile, though her eyes were closed and her head was bowed again, murmuring thanks, presumably to the Almighty.
Murphy had asked the exact question I’d needed to hear to tip me off to the answer. Help from above? I was not above taking help from on high, and given whose child was in danger it was entirely possible that divine intervention was precisely what had happened. I touched the brim of my mental hat and nodded my gratitude vaguely heavenward, and then turned to hurry back to the lab. “Charity, I presume you’re willing to donate for the cause?”
“Of course,” she said.
“Then we’re in business. Get ready to move, people. This will only take me a minute.”
I stopped and put a hand on Charity’s shoulder. “And then we’re going to get your daughter back.”
“Yes,” she murmured, looking up at me with fire in her eyes. “Yes, we are.”
This time, the spell worked. I should have known where the fetches had found the swiftest passage from their realm to Chicago. It was one of those things that, in retrospect, was obvious.
So, whoever hit Harry's car, whether with goodwill or ill intent, it had the consequence of Murphy getting involved. Murphy's involvement directly led to Harry successfully finding the opening to Deep Faerie to rescue her. And, Murphy's entrance and assistance followed directly after Charity and company sought Heavenly assistance in the matter. As to Mab, she would be fully aware of a method of how Harry would search for Molly, so I doubt she was surprised and anticipated it.
So, I agree that Mab could definitely have been the one to have fixed Little Chicago. Subsequent text in later books confirm that possibility since Fae with benevolent intent can have greater freedom of action within a threshold which Mab wouldn't have had much of a problem with anyway.
As to Murphy/Mab in some capacity at some point, it's kinda nice to think that Harry is being led by Murphy through the series with a set of probing questions. Like Hades said, "All I did was ask you a few questions," which if you go back through the early books, the conversation between Murphy and Harry is her nearly always asking him questions.
“But you’ve already helped me,” I said. “Just by pointing out what was going on.”
Hades didn’t smile, but the corner of his eyes wrinkled. “All I did was ask you a few questions. Are you ready?”
Bringing in Molly, preserves a successor for either Winter and Molly. It also bring Murphy to Arctis Tor. If somehow Proven Guilty was an attempt by the bad guys to get rid of Murphy prior to her ascension as Mab, then Mab short circuited that gambit by bringing Murphy, her prior self, to the safety of Arctis Tor. Or, if Murphy is a vessel of some kind, she is a backup.