Katy saw her brother close in on her slowly...
Cal was naked, but somehow his body was altered by the collar's curse and it seemed that a fine layer of fur had covered his body and turned his finger- and toenails into sharp claws. His eyes were gleaming eerily as they reflected the moonlight.
Still closing in on his sister, Cal started to caress his body with his fingertips only to end his tender strokes at his canine sheath every time.
Even if his body looked mostly human, Cal's maleness had shaped change completely to resemble a dog's sheath in its full glory. The tip of his changed penis already was visible and Cal was fully aware of Katy's twisted intered in it.
"Come on, sister" he growled "succumb to your heat and release my cock. I know that you long for my sperm and I'm more than willing to fill you up with it to mark you as my bitch ... to make you part of our pack..."
Katy was shivering. She felt alone. She wanted to run. To hide. But all she was able to was to stand still and stare at Cal closing in on her.
She did not notice the half-transformed Clara begging for Mark to mate with her and make her part of the pack.
She did not care for Sarah and Buster mating and howling close to the car anymore.
All she saw and felt and longed for was Cal's seed. The collar's curse, deeply rooted within her soul by now, clawed away at her humanity with every heartbeat.
As Cal had reached Katy (closely observated by his grinning pack-alpha bitch Darleen), the girl had already shed her clothes and knelt on the ground before her brother.
"Be part of our pack, be my bitch... sister..." Cal growled slowly, the human syllables sounding arkward and animal-like.
Katy only moaned in response and started to slowly lick her brother's canine cocktip while her trembling fingers caressed the soft fur that had grown on and around Cal's sheath.
With every lick of her tounge, every suck of her lips and every slight scratch of her fingernails, Cal's cock started to grow out of it's sheath.
Katy welcomed every inch of it with her tounge and lips and soon was sucking it with abandon. She tasted his precum and she felt his aroused thrusts. Soon both were moving in union and Katy's moans turned into canine whines while she kept sucking the huge canine cock Cal was now blessed with.
---
While Katy was receiving the seed that would mark her as part of the pack, Darleen wandered between her aroused 'children'.
Not counting Buster the dog (who was infected in his own special way and as loyal to her will now as anybody else blessed with the collar's magic), all of her human followers had finally succumbed to the
collar's thrall.
The teenager Sarah had changed shape into her new form completely by now and was still mated by Buster. Judging by her heated scent, Darleen could tell that Sarah was enjoying her new way of life very much.
Katy's girlfriend Clara had succumbed to the curse as well. Darleen's human son Mark had been given the honor to mark her with his seed. While Clara had been the one to lure Katy and Sarah away from their parent's house, she had been begging for Mark to fuck her in the very end. There was no escape from the curse and now she was in mid-transformation as Mark mounted her from behind, slowly turning into his dog-form too.
Darleen was proud of her childen. They had accepted their new way of life and soon they all would flock to her side to form up as a pack of all-loyal were-dogs.
Then Darleen could think of new plans to spread the curse...
---
Katy could not stop sucking her brother's slick cock and her incredible canine heat rocketed her into spheres of bliss she had never believed to exist in the first place. Cal's scent flooded her mind as much as the seed that finally gushed from his straining cock. She drank it faithfully and enjoyed it's taste while whining. Wave after wave of orgasm shuddered her body, but she did not let go of Cal's cocktip. She licked and sucked every last drop of warm cum from the doggy penis.
Finally she had found her future. She had abandoned her human self as the curse had marked her as a full-fledged were-dog.
As the heat and the arousal started to push fur from Katy's no longer human skin, the changing girl lifted her changing face up to the moon and howled in bliss.