It all followed from a late-night call that Mel took while I was in the shower. When I came out, I could see something had changed. "Tell me," I said.
"It was Celia. She says Rob has offered to baby-sit next time - if it would be OK with us if she came instead. She thinks she might be bi, and wants to find out."
"Seriously?"
"Yes." And then, carefully, "It changes things, doesn't it?"
In order to understand just how the situation would change, I need to go back and fill in the details of how our relationship with Robert had developed. Truthfully, it had exceeded our expectations. Rob told us he was the advertising manager for a large group of trade magazines, well enough paid for Celia to be a full time housewife and mother to their three children. We liked him instantly. He seemed very like us.
At the second meeting, after some promising flashing in the hotel lounge, Rob could hardly wait to get up to our room. He wanted to show us something. A picture of Celia. He had taken it with his mobile phone camera after promising his wife that he would delete it as soon as he had shown it to us. They are ultra careful in case their children get access to the phone.
Of course, we were pleased, even if discretion meant that we didn't see Celia's face. She was in bra and knickers, half reclining with one hand inside the waistband.
"Nice tits," said Mel. "Bigger than me."
"Don't be too modest," said Robert. "The way your nipples harden gets me going. I guess we all like a change."
"And Mark wouldn't mind getting his cock in between those," said Mel. Chance would be a fine thing, I thought, remembering the problems of their children.
Nevertheless, Rob had begun something that developed very satisfactorily. First, we agreed that he could take a picture of Mel and me in action for Celia to see, with the same promise that it would be deleted immediately afterwards. He chose doggy with me half in and half out, and we all approved the result.
The bonus came at the next meeting: I took along our camera and we all three took turns at taking pictures while we indulged in all the permutations we had enjoyed previously. The last shot showed Mel wiping our joint spunk from her tits with Celia's knickers.
The deal was that any shots that showed faces would be wiped - we did that together before Rob left - but that Mel and I could transfer the rest to the computer at home for our future pleasure. I have to say, there was a lot of that, and the fucking it led to was intense and imaginative. The great thing was the developing trust: we knew we had no intention of letting any photos be seen except by the three of us, and Rob believed that to be true.
In the way that one thing led to another, Mel took the initiative by suggesting we surely now knew Rob well enough that we could abandon the hotel and invite him to our home. We would have more freedom there, she argued, and could share the photos, too.
I had no problem with that. In fact, I had become a little worried about the preliminaries in the lounge. There had been one session when the two of them got carried away to the point that Rob had his cock out while Mel removed her knickers and passed them to him quite openly. Fortunately, no one walked in at the crucial moment but it made me feel we were getting a bit too bold in our pursuit of the original idea.
Admittedly, we were more than thirty miles from home but not outside commuting distance for some of Mel's pupils - or the parents she met on open nights. There was also the possibility of one of Rob's contacts turning up by chance.
Anyway, not for the first time, Mel's suggestion was inspired. Rob arrived and I had hardly poured him a drink before Mel took his hand and led him upstairs. As she does with me, she went first, knowing that a short skirt did nothing to hide her knickers from the view below. Wardrobe at home was more revealing than anything she dared wear at the hotel.
I've already explained how big a part knicker fetish would play, and how happy Mel was to indulge it (Celia, too, it had transpired). It had been clear from the very first meeting that Rob would share my delight in sexy silk across a tight arse or pressed into the crevice at the front. Or wrapped around a needy dick.
On this occasion, we had laid out on the bed a selection of the knickers I liked best. While Rob was shedding his clothes, Mel held out each pair and invited him to choose. He went for lilac green French knickers. Mel - who was already down to basics herself - stepped out of black and into green.
Rob's next request was for her to bend over, resting her arms on a chair while I stood behind her and rubbed my cock against the fabric covering her buttocks. It worked for me, and it worked for Rob: he gathered a blue pair from the bed and wrapped them round his shaft while he watched my cock slide up and down.
The spanking that followed was also less inhibited than we had felt inclined to risk at the hotel. After the third resounding slap, Rob was anxious. "Is this good for Mel?" he asked.
She answered for herself. "Don't worry. It sets my juices flowing. And we'll stop soon. We want you to see the photos."
Once Mel had taken her spanking and been released from my lap, we all sat together on the edge of the bed. I had my laptop set up to provide a wi-fi slide show to the big TV screen on the facing wall. We do sometimes watch Newsnight while in bed, or maybe a movie. Porn, too, of course - our favourite overture to our own performance.
Now, as the screen came to life, the first shot was of Mel's arse, black knickers, bent over. It elicited a little gasp from Rob, remembering the occasion - "Oh, yes." - and his hand flew to his dick. By the time of the dissolve into a shot of Mel's mouth wrapped salaciously round my knob, he was erect and working hard at maintaining it. He had retrieved the green knickers, which were clearly helping. Then he realised that by looking to his left he could see the real Mel mirroring the screen.
I had set the slide show to its slowest rate. There were twenty-seven photos. As each one appeared, Mel and I followed its example. Whatever Mel and I did on the screen - sucking, fingering, sixty-nining, fucking, me on top, then Mel riding me with one hand on her clit and the other tweaking a nipple - Mel and I did on the bed.
Some idea of how successful this was can be understood if I say we were on shot twenty-three the second time around (a vigorous doggy) when Rob couldn't hold it any longer and shot into the green knickers. That triggered me. In the next photo I was in Mel's mouth, and that's how it ended.
Later, having sent Rob happily on his way to report to Celia, we reflected on a very successful session. I was aware that, at the end, Melissa hadn't come, but we were planning to rectify that shortly. First, I had a question for my wife. "When we were all getting carried away, you had your eyes close while I was piling into you."
"Yes, and very good it was, too."
"But I did just wonder if you were thinking about how it might be if wasn't my cock, but Rob's"
Mel thought for a while before answering. "If I'm honest, I can't say that it was in my mind at that moment. But if not, then at some other time. Yes."
"What would you have done if I had offered the possibility?"
"Nothing. You know that. If we haven't agreed beforehand, nothing happens."
"But suppose I say now, it would be OK next time?"
"It would still depend."
"On?"
"On whether it was something you could cope with. Whether it would be good for you to watch. Good for both of us."
"I've ben thinking about it."
"So have I."
"And?"
"I think it might happen. But not yet. It's too soon for all of us."
"If you think so, you know I trust your instincts."
"But," said Mel, "there might be a compromise."
I was immediately alert. Mel didn't say such things lightly. "Such as?"
"Suppose next time, you have me from behind. Rob is in front of me, watching and wanking in a pair of my knickers."
Easy to picture. We've been there. "Yes."
"But then I ask him to drop the knickers and offer me his cock."
"In your mouth?"
"Yes."
I didn't need to answer. Mel put her hand on my cock and knew what I was thinking.
"Is that a serious idea for next time?" I asked.
"Maybe. But you can see where that leads. You and Rob switch places, and now I'm being fucked by Rob. Are you ready for that?"