As you re-enter your house and sneak up to your room, the last trace of the bitch you'd almost become fade away. Quickly getting dressed, you storm back downstairs.
"hey man..." Dave said looking up from reading the paper on the couch before a concerned look moved over his face at the sight of you, "You ok man? You look like you just ran a marathon" Indeed, you were still sweating from your encounter and the shock of the transformation.
"Yeah...yeah...I'm fine..." A movement by the doorway catches your eye. It's Duke, cowering. "You know Dave...we really should get duke fixed.."
-o-
Duke panicked and ran, "Shit, what am I gonna do now?!" It wasn't just the loss of unlimited sex and the probable loss of his tentacles that he was upset over. The collar had a much greater effect. It would allow the male dog to transform the female between her human and bitch forms whenever he wanted, and gave the male almost total control of the female's mind and body...after the initial mating.
But the greatest loss was that of life, your life to be exact, for the final, and most powerful effect of the collar, was that, as long as the female slave remained alive, the dog would feed of of thier excess life force, keeping him from ageing.
But, just as Duke was about to give up, the air shimmered in front of him, and the collar, which had copied itself after being used to turn Mark into Butler's "Maid," fell to the ground at his feet.
"Yes! She linked it to me!" Duke practical jumped with elation. The dog-woman at the store, one of his litter-mates who had, by magic, risen to anthrohood, had changed the enchantment on the collar.
Normally it was to be used once, and only once, to create a single bitch-slave. But, thanks to the spell, it would copy itself after each transformation, leaving once copy behind to become a normal collar for the new bitch, and the other to return to Duke for him to create another slave.
Duke picked up the precious treasure in his mouth and quickly hid it, he'd have to wait for both you and Dave to fall asleep before he could use it. He could influence an unaware mind to put it on and initiate the transformation, but couldn't do it to someone who was aware of what was really going on.
Once you were asleep however, he could simply place the collar on you (or Dave), focus his thoughts on wanting you to put it on, and your body would put it on automatically, you might not even wake up until he'd already fucked you and made you his slave.
The only question now was which one of you he would transform first...