This is what I picture...

We only have a few minutes left to wait, if he's on time, and my nerves are singing with anticipation, fear, and desire. For the last half hour at least I've been entertaining visions of what's about to happen that create surges of jealousy—it can't be called anything else—in my body at the thought of sharing you. Why didn't this occur to me before? I start to have an inkling of what the swirl of your emotions mostly feels like, and that only makes me more frightened. 

As befits my position in the upcoming scenario—we agreed on this—I'm mostly undressed, wearing only a stockings and garter set and some very sheer lingerie. You're looking quite smart, in contrast, and I suddenly can't resist the urge to crawl up on your lap where you sit passing the remaining minutes on your PC, squirming my naked, silk-clad, and nylon-covered skin against your legs and chest. I suddenly wish he weren't coming. I try to straddle you. "Sweetheart, why don't you go brush your teeth," you suggest, firmly setting me back on the floor and nudging me in the direction of the bathroom.

This is supremely irritating. I am already immaculately clean and I am not in the mood to be ordered around like a little girl. But I can't risk putting you on edge over something stupid right when you're about to do this incredible thing at my request, so I pad unprotestingly to the bathroom. I take my time and concentrate, and the process of brushing my teeth soothes my nervous energy, as you must have known it would. Almost as soon as I finish, the buzzer goes.

Our eyes meet. My heart suddenly pounds. I can't read your expression when you buzz him up—but you're not smiling. You push me into the center of the room in easy eyeshot of the door. When I hear his footsteps on the stairs my face floods with color, but when you answer the door, and I see the expression of nervous anxiety on his face, I forget my own embarrassment. I jump forward unhesitatingly, reaching out my hand and smiling, and introduce myself with the same kind of friendly smile I'd use with a new acquaintance on the street.

"I'm Ben. Nice to meet you too," he says in reply. His eyes flicker over my body, but I notice he seems mostly concerned with your more imposing figure. Well, I can't blame him for that—while he responds to your offer of a drink, I examine him covertly. He's wearing jeans and a tight t-shirt, plain gray, with a jacket over it. He's shaved his face smooth, and slicked his hair back. He's only slightly taller than I am, and while his shoulders are indeed wider, his build isn't strikingly bigger than mine either. However, his muscles, from what I can tell, are well-defined. There's a hint of acne on his skin, but he looks healthy, and I can smell him from here—fresh soap, and the leather of the jacket, and something sweeter. His face isn't classically handsome, but his eyes are a delicate gray and his lips are full, expressive, and sensitive-looking.

I have already asked him lots of questions, and received his replies, coming back and forth through email. I know he's had top surgery and been on hormones more than two years, and that he usually doesn't want to be naked from the waist down but it depends on his comfort level. I didn't ask him if he would be packing or not. You belted me so viciously when I mused dreamily out loud about the potential of his having a big, hard, sexy strap-on cock for me that I thought it would be best to let the subject drop after that, and just let him show up and surprise us. Based on his Craigslist ads, I thought it more likely he'd try to entice you with whatever female parts he had left. He really wanted a spanking. 

Both of you have sat down in chairs in the kitchen and I spring into action making you each a drink. You are interrogating him, and it starts out easy and relatively impersonal, but soon, while you sip, he's required to tell you whether he's been spanked before, what arouses him about that scenario, what scares him about it. He drinks too fast. I have slipped to my knees next to you, but after a few minutes I slide over to his side of the table and gently reach for his hand where it's fidgeting nervously on his lap. I lean my cheek on our linked fingers, against his leg. I can feel him tense in surprise, but my eyes are on yours, which darken threateningly for a moment. 

"Isn't she a sweet and lovely little girl?" you ask Ben, your teeth gritted slightly. 

He seems to have recognized the danger in the situation. He replies cautiously, "Y-yes, she is."

"Now, I think it would be very nice if you called me Sir while you’re here.”

“Yes, Sir,” Ben says immediately. His fingers flex against mine.

“Good boy. Finish your drink. Then come over to the bed. Angel, you come with me.”

I get up and follow you, grinning from ear to ear. I’m absurdly proud of you. You’re brilliant. The perfect Daddy.The perfect master of this situation. You even said “good boy” to him! As your turn around to face me, I come forward, eyes shining, ready to hug you or somehow express quietly my approval.

The blow is unexpected and your powerful slap knocks me sideways onto the bed. Before I can even struggle up, your hand is in my hair, pulling hard, and my eyes fill with tears from pain and surprise as they meet yours.

“From now on, slut,” you hiss, “you ask before you touch him.”

My mouth falls open. “Yes, Daddy!” I gasp quickly.

You use my hair to yank me onto my knees next to the bed. I can see you sitting down on the side of the mattress out of the corner of my eye as I stare at the floor, trying to compose myself. I feel like crying—how could I have screwed up this soon? How much of that did Ben watch, and what was he thinking? If it wasn’t clear before, it’s obvious now who is at the bottom of the status hierarchy in this odd three-person relationship. My chest is tight and I have to take deep breaths, but after a minute I get myself under control and manage to look up.

       Ben is standing in front of you in the middle of the floor—you must have beckoned him over. He’s taking off his shirt. His chest is beautiful and I immediately stop feeling sorry for myself and start feeling proud and happy for Ben. He shakes a little as he undoes his belt and slides his jeans down over his hips, then steps out of them. I look keenly at his crotch from under my eyelashes—but I can’t tell if he’s wearing anything there or not. Then I feel guilty for fixating on it so much.

       “Come here,” you say softly, and I feel my pussy ache in response even though you aren’t talking to me. Wearing only a pair of loose boxers, Ben shuffles forward until you catch him by the arm and pull him skillfully over your lap. You’ve done this to me countless times but I’ve never witnessed it, and now I watch with undisguised admiration. Ben’s head is resting on the bedspread, his arms up by his face, and his feet are toeing the floor on the other side of your legs. His tight butt looks very cute perched over your knees. I’ve turned sideways for a better view and my eyes are wide and staring. Ben’s head is turned away from me.

       You rest one big hand on the cotton covering Ben’s rear. I hear a small sound escape his throat. I know he’s fighting the urge to shift his hips on your lap. He wants it. “Now, little boy,” you say, “I want you to clasp your hands together behind your neck. Good,” you continue as he does as ordered. “Don’t you dare move them.”And without further delay you land the first swat over his boxers.

       Ben grunts in surprise at the first smack, but settles into it as you continue for several more blows. I know from experience you can hit much harder than this. You’re warming him up. You are focusing on what you’re doing, your eyes on his upturned ass. But after about 15 swats, you suddenly look at me, and your gaze is so intense my breath catches in my throat.

       “Tell me you’re a filthy, depraved little whore,” you growl at me, your hand poised to fall.

       My face floods with heat and my eyes fill up again. I don’t want to do this now—not in front of the new person. I don’t want to stoke your anger this way. Humiliating me while you are giving this young man his fantasy just seems so cruel and unfair. Can’t it just be about Ben for a minute? But I know this is not a scenario you would have ever chosen—I must please you, and I want to please you. It’s so hard, though…

       “Tell me, sweetheart!” You almost shout it, and at the same time you yank Ben’s shorts down below the cheeks of his ass. I see him clenching them together and his hands start to come down to cover himself. You stop that with a hard spank, your hand cracking down viciously on his bare skin. He squeaks and jerks his hands back into place. He liked the way it felt.

       “I’m—I’m—“ I whisper, miserably.

       Swat! Swat! Ben starts to wriggle. “Speak up, angel.”

       “I’m a filthy, depraved whore,” I choke out. I shift uncomfortably on the hard floor, heat pooling between my legs, my focus dimming to everything but the sound of your hand on Ben’s vulnerable skin and the fire in your gaze.

       The spanks are falling hard and fast now. “And a dirty little bitch, aren’t you, slut?”

       My eyes dart back and forth between Ben’s reddening cheeks and your stern face. He is starting to kick a little. “And—and I’m a dirty little bitch.” My face gets hotter, if that’s possible, and one tear escapes.

       “That’s right. What kind of dirty bitch would like watching something like this?” As you speak, you punctuate each word with harder and harder swats to Ben’s ass. Finally he cries out, his hands breaking their hold again, but not going so far as to try to reach back and protect himself. You switch your attention fully back to him. “Oh, does it hurt, little boy?”

       Fortunately, he seems to know he’s supposed to answer. “Yes, Sir,” he mumbles, his face in the comforter.

       This spurs you to deliver another flurry of swats, until he does break and bring his arms back. This is an opportunity for you to use your strength on him, and I wonder if he knew that. You pin his outside hand with your left hand and continue to spank him until we can both start to hear the snuffling sound of his first tears.

       Immediately, you push him off your lap so he rolls onto the bed. You stand and go after your unfinished drink. He takes a shuddering breath and wipes his face, lying on his stomach with his ass still exposed. I look at him, then uncertainly at you, standing some distance away, an inscrutable expression on your face. I get up with sudden decision and move towards you, close enough to whisper, “Please, Daddy, may I comfort him?”

       “Oh, what a sweetheart,” you say, and your voice has a hard edge that makes my heart beat faster. You reach into the cup of the sheer bra and pinch my nipple hard enough that I whimper and reflexively clutch at your wrist. “Keep it above the waist, for now.”

       Nipple smarting, I return to the bed and sink down gingerly next to Ben, who is watching me, his face turned to the side. I carefully rest my fingers against his hair, then run them through it when he seems to accept the touch. I brush my hands over his face where it is still wet from his crying. I smile at him and murmur, “It’s so good, isn’t it?”

       I don’t get an answer, because as I start to stroke his shoulders you are suddenly there behind me, and your hands are in my hair again. I cry out as you forcibly shove me into position kneeling on the bed over Ben’s sprawled legs, ripping off the frail panties I had on. I catch myself on my forearms, my face hovering over his reddened, exposed ass.

       “What a nice red bottom,” you comment, and both of your poor victims squirm in humiliation. I see Ben’s hands clutch the comforter, the same as mine are doing. “Spread your cheeks for her, little boy.”

       I can’t imagine anyone could feel more embarrassed than I do right now, but Ben must. You are still holding my head imprisoned by the grip in my hair, and I watch helplessly as the young man trapped under my kneeling body reaches hesitantly back to his fiery butt and starts to grip the cheeks in his fingers. He pulls them slightly apart and I can just glimpse the tiny dark hole in between, surrounded by a sparse growth of hair. I can’t see much below the curve of his buttocks where the elastic of his boxers still rests; it looks shadowy and hairy there, and mysterious.

       “Wider.” He makes a sound—I can’t tell if it’s a sob or a pleasure cry, but he obeys. My head is spinning—I’m amazed by you—I never dreamed you would go this far with him…

       Your finger thrust violently into me makes me squeal and try to wiggle away, but you have found me wet, and you pump my tight pussy mercilessly for a few moments until I moan, muttering, “Such a disgusting little slut. So wet looking at another man’s asshole.” Your well-moistened finger next goes fast and hard into my own ass, and as I gasp, you start to force my head down and order in your sternest tone, “All right, princess, you know where your pretty little face belongs. Get that slut mouth to work.”

       My face is shoved abruptly into Ben’s dry, hot crack. For a second I am frozen in shock, though I have known this was coming since you moved me into position here on the bed. I realize after a few seconds that Ben had moved his hands, but now they have returned to their place holding his cheeks apart—you must have corrected him. When you remove your hand from the back of my head and release the pressure, I lift up enough to draw a deep breath, then tentatively put out my tongue just as you plunge your cock into my ass.

       Involuntarily I shriek and throw my head back, trying to crawl forward away from the punishing presence of you inside me. You have a firm grip on my hips. “Get back to work, slut!” you remind me in a growl, and, groaning, I force myself back into place with my face between Ben’s cheeks. I lick gently at his hole, thrown off at first by the powerful thrusts rocking my body, and the wiggling I can’t help as your size causes my belly to cramp. But within a very short time, as always, the pressure in my ass starts to feel good—unbearably good, and I’m rocking back against you, breathy cries escaping my mouth even as my tongue probes Ben’s hole in rhythm with this fucking, the feel of his tight rubbery flesh and its musky sweet taste its own pleasure.His hips, too, have started to move, and with my last bit of presence of mind I notice his fingernails are digging into his sore skin where he’s holding his cheeks apart for me. My scrabbling, grasping hands make me aware of this and I brush his fingers aside, kneading, squeezing, and punishing his already-beaten ass while my tongue worships the forbidden little hole.

       “Uh! Uh!” I hear him start to cry.

       I try to raise my head enough to beg permission to come, getting as far as a muffled, “Daddy—please—” before you reach forward and shove my head hard and viciously into Ben’s crack, holding it down and beginning a brutal pace of thrusting while you growl, “Go ahead and come, sweetheart. Come while you eat another man’s ass. God, you slut—!” I go over—I grip Ben’s cheeks hard and push my tongue as far as I can into his asshole while I clench white hot and helplessly on your body. I can’t breathe while my body spasms over and over again, and I can dimly feel your come shooting into me while my own spend runs wetly down my thighs. And then Ben’s hole is shivering and spasming too, trapping my tongue, and your hand is still on the back of my head, and at last I start to panic and struggle for air.

       You let me up and I collapse on my back on the bed, breathing hard, next to Ben, who is still facedown and now burying his head in his arms. A few peaceful moments pass. Just when I start to worry, he reaches back and pulls up his boxers, then sits up. He’s smiling—a little shyly, but he looks pleased.

You’ve fixed your clothing and look completely self-assured compared to we naked, sweaty, and discomposed sluts on the bed.  “Thank you, Daddy,” I say, gazing up at you, and I mean thank you for letting me come, but also for everything, for all of this, tonight.

It prompts Ben, who chimes in, “Thank you, Sir.” I turn my smile on him and can’t help giving him a little wink.

“Go wash your face, princess,” you say to me, and I realize you’re ending our evening with the newcomer. I get up as gracefully as I can and turn to shake Ben’s hand one more time, saying, “It was very nice to meet you.”

I take my time in the bathroom, my stomach knotting with tension again already. Ben is probably well on his way home by now, but tonight is probably not over for me yet. If I’m right, I’ll be paying for this little fantasy-come-true with a session with your belt. Well, is it so much to ask to appease my marvelously accommodating Daddy, who has just spanked a man for me?

By the time I emerge, stepping with trepidation back into the bedroom, you’re sitting patiently on the bed and you’re already holding your belt and your ruler. My heart thunders, but before you can stop me I run towards you and jump into your arms. I shower kisses on your face and neck. “You are truly the best, most awesome, most impressive Daddy in the whole world!” I whisper, snuggling my naked body into your broad chest.

“Well, I’m glad you had fun, sweetheart,” you say, sounding like you want to laugh. “Now come and bend over the bed, so I can remind you just how earnestly I dislike sharing you.”