My wife, Sherry, is generally quiet and proper. But even so, she absolutely loves sex with me, though in a sweet, affectionate way. She actually can't seem to get enough. But there have been a few times that she has *really*surprised me. The first time was before we were married. We had been living together a few weeks and were really getting along well. One night after we had just turned in, she grabbed my head and kissed me. That may not seem like much, but Sherry was usually more passive about sex. This night, though, she let go and went after me and once we were at it, she amazed me with her attitude: she gets excited and often moans when we have sex, but this night, she talked to me more, saying things like "Oh, yes! Real hard! Harder! Please!" She also grabbed my body and pulled me into her. Believe me, I had no complaints!

After we both came, we lay there in each other's arms, and soon she was nibbling on me and giving me a sly giggle. I couldn't believe it! She wanted more! I couldn't figure out what had gotten in to her, but I was sure to oblige.

Except that I heard a noise in the house--a suspicious noise. I got up to investigate. I whispered to Sherry that I was going to investigate a noise and she grabbed my hand and asked me to stay. But that noise had bothered me too much so I wasn't going to be stopped. Then Sherry got up and got in her robe and came along. She said she wasn't going to sit there all alone.

I checked around, and when I got to the guest bedroom, I got one of the surprises of my life! There was a nude woman in there, tied up, blindfolded, and gagged! Sherry and I looked at each other, and then she started talking, nervously and rapidly. She said it was her sister Sheila! The woman was trying to say something and was obviously trying to escape. She was lying face down on the bed and had gotten her knees to the floor, but her feet were tied together too well for her to get any further. Sherry reminded me of how she had a twin sister and how she had warned me that Sheila couldn't be trusted. She said that Sheila had come to visit... actually, to make her sister miserable and that Sheila would do anything to steal me from Sherry. She said she finally had to do this to protect her own interests.

My jaw dropped. I had never suspected that Sherry would do such a thing. I told her I was going to untie Sheila, but Sherry was adamant--she insisted that if that woman were untied, she would do absolutely everything she could to get me away. She said Sherry and Sheila knew each other well and I shouldn't worry about this. I don't know how, but somehow she convinced me to leave the woman tied.

Then Sherry really surprised me. She said I should give Sheila what she was looking for--to do her ass right there! I realized I didn't know Sherry as well as I thought I did. But family relationships can be very revealing.

Sherry continued to insist that I do Sheila's ass. Sheila had started trying to say something again and was squirming a lot. I told Sherry it would be rape. I was still mystified by the way Sherry was acting that night. Sherry said it wasn't rape because Sheila definitely wanted my cock. In the ass. It didn't look right to me and I told Sherry so--Sheila was still struggling and saying something. Sherry said I should massage Sheila's cunt, and only take her ass after she got excited. She said if Sheila started getting excited and wiggling her ass in an inviting way, I would know she wanted it.

Well, I told her I wouldn't do it unless it was obvious Sheila wanted it. But I started caressing Sheila's cunt with my fingers. Sherry told me to make sure they were wet and to make sure I fingered Sheila's clit. She kept on giving me very explicit instructions. Sheila had stopped wiggling and seemed to be resigned to the caresses. Soon I felt her wetness. Sherry actually put a finger on Sheila's cunt to check the wetness herself! Sherry told me to frig her faster. Soon I heard Sheila's breathing grow heavy. Sherry gave me a tube of K.Y. and told me to get Sheila's ass ready with my fingers. It was happening! Sheila was wriggling her rear and pushing it towards me! She looked like she was out of control!

I slipped lubrication into her rear hole with my finger. She pushed back on it! Sherry was watching closely and seemed amused! It still strikes me as so weird that Sherry would be so interested in such kinky stuff, and that she would ever think about me having sex with any other woman, much less her sister.

Finally, Sheila was so hot, I thought she was going to go crazy. Sherry told me to go to it. I was hard, but Sherry helped me along with her hand anyway. I couldn't believe this was happening! I put the head of my cock right on Sheila's rear hole. Sherry got down next to her and whispered in her ear. I pushed. It was so tight and felt so delicious! I gradually pushed it further, and soon had it pushed all the way in. And Sheila was pushing back against me as if she wanted more! She started pulling away but stopped and pushed again. She wanted me to fuck! I started slowly and then gradually worked up 'til I was fucking it with abandon! Sherry was giving me encouragement, like "Fuck that little slut! Give it to her good! Give her what she deserves! She wants it, the little slut! She needs it!" It was so different from the way Sherry usually acted.

Finally I was coming, and it was obvious that Sheila was too. Sherry was frigging herself under her nightgown and came too, so we all came just about together! Afterwards, Sherry dragged me back to bed and she was still horny! I was worn out though, and we played with each other and kissed, but I wasn't hard enough to get it in her.

The next morning, Sheila was gone by the time I got up! Sherry was already up and told me Sheila had left. She seemed exhausted, and I noticed that she seemed even quieter and more reticent than usual for the next few days. I figured that alcohol had loosened her inhibitions for one night and now she was embarrassed by the whole thing.

But I sure thought about Sheila. It was weird that the only time I had "met" her was under such circumstances. The next time I met her was even weirder than that first time, if anything. I was off to a trade show for a week, but ended up coming home after just two days because it didn't turn out to be as useful as I had hoped. When I drove back to my house, there were a couple of cars there that I didn't recognize. Well, when I walked in, Sherry met me at the door and insisted that we immediately go out for dinner. Though I was a little tired from my trip, I was willing to relax at some place casual and that's what we did. At the end of dinner, she told me that Sheila was back. I was amazed and noticed that Sherry seemed to be watching me closely. We went home immediately. I noticed that one of the cars I had seen before was gone. Sherry told me the other one was Sheila's. We went in and Sherry took me to the guest bedroom. Along the way she told me not to say a word. Sheila was nude and blindfolded again. But she wasn't tied up--she was kneeling-- sitting on her heels on the floor. And she wasn't gagged either. Obviously she could get up and remove the blindfold whenever she wanted to.