It had all started off as a normal hunt, well, as normal a hunt could be with Cas tagging along. Neither Dean or Sam had questioned why Cas had turned up in their motel room a month ago and never really left, joining in with their hunts. They never asked because they knew the reason, knew that Heaven wasn't exactly a fun place for Castiel to hang out anymore, that Castiel finding his own identity and free will had opened his eyes to the corruption that happened up there. Sure, it was kind of odd waking up in the middle of the night and Cas just being there, or the fact that he would trail their every move, almost as if he were worried they were going to disappear on him. Dean would sometimes see a look in Cas' eye, of pain and gratitude all mixed into one, of complete and utter devotion to the two boys and Dean would always look away because it hurt too much to think that this angel was living his life through them, that they were the only people he had in his life now, the only ones he could trust. No, Dean chose to ignore it, pretended that it was normal for Cas to always be there with them, that that was the way it had always been. And Sam and Cas played along with it too, Cas never opening up to why he was always there, and Sam just carried on being Sam, the nerdy younger brother.
Yes, it had all started with a normal hunt, a town distressed with horrific deaths, of couples turning against each other, children killing their parents, the usual crap that Dean and Sam always dealt with. Within an hour of looking at the latest crime scene they found the hex bag, and Dean had grumbled and complained because he hated witches and the sooner they killed the bitches the better. Cas had used his angel mojo to locate them and stated that there were three and they were definitely the culprits, zapping Sam and Dean to the building without a warning.
They had gone charging in with their weapons, unafraid, because hell, what could three witches do against two hunters and a freaking angel of the lord? Turns out, a whole lot more than they bargained for.