House sitting surprise

Some friends of my wife had booked a trip away for the weekend and asked her if she would mind house sitting for them. Their pride and joy was a two year old Neapolitan Mastiff that they didn't want to put into a kennel. As they lived an hours drive from our house we took them up on the offer to stay at their place. We more happy to help and since their house was very nice we thought we would have a romantic time as well.
We arrived on Friday night and were given all the instructions and our friends left soon after. We had seen Roy the mastiff a couple of times before but he had grown to almost full adult size and was a huge drooling grey energetic dog. He lived in the house with his owners and was well trained although the little bit of pup left in him still got him quite excited whenever guests arrived.
After we settled in we had a couple of drinks and thought it would be nice to use the spa in the master bedroom en suite. We started the water running and stripped off. Cheryl wrapped herself in one of the towels which I found amusing since it was only me and Roy in the bedroom but she said she felt weird being naked in front of Roy, who at the time was lying lazily at the bathroom door on the carpet of the adjoining master bedroom. I left her to go and refill our drinks and when I returned I sat on the edge of the spa while she was swirling the water with her hands as it was filling. I took the opportunity to slide in front of her and she readily took my cock into her mouth. I reached down and lifted her towel over her hips and worked her pussy with my fingers while she sucked me. While this was happening Roy had come into the room and was now approaching Cheryl from behind. I had noticed his presence but had thought nothing of it. Cheryl had no idea he had come into the room and I didn't tell her either. I watched as he approached even closer until his massive face was right
near Cheryl's exposed pussy as I continued rubbing it. I found this very exciting and spread her lips apart with my fingers. Roy's gave a couple of little sniffs of her pussy and them his long wet tongue slid out of his drooling mouth and took a long slurp between Cheryl's open flaps.
At first there was no reaction from Cheryl but Roy's second lick of her pussy made her freeze as she realized that it couldn't possibly be my fingers. By the time she knew what had happened Roy had lapped at her pussy a number of times before she spun around to see what had happened. She was shocked when she saw Roy standing there and was very pissed at me for not stopping him. I told her that I didn't think there was any harm, and he wasn't about to tell anyone. She calmed down and escorted Roy out of the room and wen back to our spa.
I asked her how Roy's tongue had felt and she said it had been nice until she realized what it actually was. I asked her what would have happened if she hadn't known and she agreed that she would have most likely let it continue. She either enjoyed it more than she admitted or the thought was turning her on because we had a very wild fuck in the spa that night.
The next day we lounged around the house all day. Cheryl had forgiven Roy for his little indiscretion the night before and even took him out for a walk. Maybe the fact that his tongue had been on her pussy had given her a new bond with him. It wasn't his fault after all.
That night we repeated the spa again and after much wine we settled on the spacious sofa in the living room and watched TV. Roy was sleeping on his own chair across the room.
Cheryl loved to be massaged, specifically her back and her feet. Our usual routine was that I would massage her for an hour or so and then she would suck my dick in return with her d cups hanging onto my inner thighs (which I loved), before finally fucking each other. I had done my part and she had now moved onto the floor in front of the sofa and was blowing me slowly while I held one of her ample breasts. My mind drifted back to the night before and Roy's tongue in Cheryl's pussy. I wanted to see it again so grabbed the massage oil and sat forward to rub her back so she would stay on the floor a while longer. I lotioned her up and massaged her for a while as she rested her head on my leg. Once more I worked my way to her pussy and gently rubbed the oil into the shaved folds. Once I felt her natural juices flow I reached for the TV remote and switched it off. The sudden lack of noise woke Roy up and I hoped he would be awake enough to come and see what we were doing. He didn't move at first so I silently patted the cushion beside me, beckoning him to come over. He slid off his chair and walked over towards us. As he walked past Chery I reached for his snout with my wet hand and smeared Cheryl's pussy juice over his drooling mouth. He licked my fingers as I drew him closer to her until he located the source once more and his tongue moved to her oiled pussy.
Cheryl lifted her head again only this time she knew what it was. Before she could say anything I guided her mouth down over my cock hoping that she would not freak out. I could feel that her body was tense as Roy flicked his tongue up and down her slot but she didn't move away and slowly started to relax. I reached my hand down over her ass again and found that the mix of her juices with Roy's drool and massage oil had allowed him to probe inside her and she was starting to breathe heavier as a result.
It was at this point that I noticed Roy's cock had come out of it's sheath and was glowing red and hard. it slapped around beneath him as he shifted his weight from foot to foot becoming seemingly agitated. In one swift move he put both of his front feet up on the lounge, causing me to reel back as his huge head almost knocked me over. I though he was done licking and wanted to be patted at first until I heard a loud exclamation from Cheryl. I could not see her beneath Roy but when he started humping I knew he was fucking her. I moved out from under her and her weight was now supported by the sofa cushions. Roy was shafting hard and fast by the time I moved to position where I could see what was happening.
The massive red cock was deep inside her and all I could see was his huge balls hanging outside the entrance to her cunt. His cock would have slipped straight into her with all the lube that was there and his knot had now swollen inside of her. He had stopped fucking vigorously and I knew he had come inside of her. I asked Cheryl if she was ok and although out of breath she said she was. In a shallow voice, she whispered that he had made her cum and rested her head on her arm. I told her that she may as well enjoy it because she was stuck there for now. I sat in front of her and offered my cock once more. She took it readily and sucked me as Roy loomed over her with his shaft still inside her. She stopped sucking after a short time and climaxed again as she told me she could feel his hot cum squirting into her again.
This continued for another 15 minutes until finally Roy's knot subsided and his cock plopped out of Cheryl's pussy. I immediately put my own dick inside her and fucked her as Roy's cum flowed out of stretched pussy. I pumped my own cum into the mix before we both collapsed onto the sofa in silence.
It had been an experience that we hadn't expected but tone that we had both enjoyed immensely.