After that experience, Catherine and Brian found themselves leading three different lives together. When they were out and about in public, their cover story had to remain intact - she was strictly forbidden from doing anything that might let on that she wasn't an ordinary dog. At home, those rules were relaxed, and their domestic life together was closer to a normal marital existence, except where one of them was lacking opposable thumbs. And in the bedroom... that was another life entirely. What happened in the bedroom stayed in the bedroom - for both of their sakes, it needed to.
Catherine always seemed unflappable, switching between these different roles. Brian found it much more difficult. Outside the house, his head was on a swivel, always expecting someone to suspect the two of them of something.
It got worse when, at Catherine's request, he took her to the local dog park. She was totally enjoying herself, running around and playing with the other dogs. But Brian soon realized, as he watched them from a nearby bench, that he couldn't leave the sexual element of their relationship at the back of his mind like he needed to. He found that he wasn't just attracted to Catherine's canine form, but to all the other female dogs as well. He could smell something on them like he had never smelled anything before. And even stranger was the way he started looking at the male dogs. Something told him they were rivals that he needed to watch out for, jealously guarding his wife and any other bitches from them.
That night, he plunged himself into Catherine's hole more greedily than ever before. It was starting to feel natural - she no longer insisted on lying on her back like a human. As he was thrusting into her from behind, the animalistic noises escaping from her muzzle started sounding, to Brian's ears, more and more like words.
"Rrrrngh, yes! Fuck me harder!" Catherine growled, in a voice that didn't sound much like her human self. To Brian's ears, it barely even sounded like English, and it took him a moment to register the fact that he had understood her perfectly.
"Wait... honey, you can talk?!" he responded, in a mixture of confusion and joy.
"Huh? Oh, wait, thank god! You can finally understand me! I was wondering how long that would take. I thought you'd have to get a lot further along than this."
"What do you mean?" Brian replied. "Is your... change starting to wear off now?"
"No, silly!" Catherine's head had turned back to face her husband by now, and she was surprised to see the blank expression on his face. "You seriously haven't noticed what's happening? When was the last time you looked closely at your fingernails?"
Brian had to admit, he hadn't spent much time worrying about his personal grooming, or even the basic elements of his appearance, ever since his wife came home in a fur coat. His mind had been preoccupied the whole past week with a lot of complicated thoughts. Now, as he lifted his hand to take a look, he was shocked by what he saw. The fingernails were so dark, they looked as though the skin underneath was bruised. They had started to change shape into sharper points. And they were surrounded by unusually thick tufts of whitish hair that looked nothing like the follicles he was used to. Okay, he might have been preoccupied, but there was no way he could have gone days without noticing this. This had to be new, within the past few hours at most. Of course, the timeline was hardly the most important thing here, Brian reminded himself. More pressing was the fact that it meant...
"Oh my god," he finally spoke out loud. "It's contagious?"
Catherine's tail, seemingly involuntarily, started wagging - a motion which reminded Brian that he had neglected to extricate himself during this sudden turn of the conversation. Despite the shock of what he had just learned, his erection wasn't weakening, and neither was his arousal. The thought that he was going to be turning into a dog just like Catherine disturbed him, but on another level it inflamed his mind and only turned him on more.
Brian tried to push back those thoughts and think rationally about this. "But... we can't both be dogs," he protested weakly. "People will find out what we've been doing!" Each potential problem that occurred to him led his mind to an even worse one. "I can't leave the house like this!" And yet, all those complications made his dick throb even harder against her inner walls. "And if I can't go to get help, then we- we're both going to be stuck this way!" But disturbingly enough, he was starting to think that maybe he actually wanted that...
Catherine heard out his increasingly frantic concerns, but then she just giggled. "Relax," she said. "Trust me. I was worried at first, too. But once you've really experienced living as an animal, you're not gonna want to go back. And we can make it work, no matter what happens. We could just run away. Find some nice family that wants to take in two strays. You always wanted to start a family, right? We'll raise a whole bunch of puppies together."
Now she was just teasing him. Catherine could see that he was on the verge of passing out from the pleasure, and she needed to encourage him somehow to keep it up, to finish the job. "Come on, we can do it right now. Your sperm is probably already turning canine as we speak. Fill me with your puppies."
That was enough for him. With a shuddering groan, Brian fell forward on the bed, overwhelmed by raw emotion and completely spent of all his energy. But he didn't fall freely, and he immediately noticed what was pulling him to the side - he was still stuck fast in Catherine's vagina, and his penis wasn't coming out even though it had blown its load and started to shrink back.
Catherine recognized the cause immediately. "Wow, it must be working really fast on you," she said with a wolfish smirk. "You've already got a knot."
Brian couldn't even muster the strength to look down at his changing crotch. He passed out right then and there.