When the doorbell rang, I was belly down on the bed — with my mouth pressed to Della’s pussy as I tongued her swollen clit.

“To be continued,” I said, wiping my mouth on the arm of my T-shirt.

“Kiss me,” she said. I obliged — moving my face to hers, tangling tongues and giving her a taste of her sweet pussy.

The doorbell rang again.

“Christ, somebody’s eager, isn’t he?” I forced myself up and off the bed and grabbed my robe.

“Rob, your dick is all stiff,” said Della.

True enough. It was tenting my sweatpants. “You’re not going to answer the door like that, are you?”

“Why not? Benny needs to know we’re not kidding around here.”

“Say Ben, not Benny,” she admonished me. “What if it’s not him?”

“Who else could it be? Anyway, this hard-on’s already losing steam.”

I got to the front door as the bell rang a third time.

Yes, it was Ben. No longer Benny. He was sharply dressed, and he came bearing a bottle of champagne. I let him in.

“Let’s get you a drink, OK?” I led him to the bar in the dining room.

He laughed and said, “Seems like it’s you who needs one. You sure about this, man?”

I ignored his question. He wouldn’t be there if I wasn’t sure.

“Should I open what you brought?” I asked, taking the champagne from him.

“If you want. Or…”

“You want scotch, don’t you?”

“Yeah,” he said with a grin. Ben loved the good stuff. I gave him a tumbler of the best I had in stock.

“I’m pouring one for myself, too,” I said.

“Make it three.” Della had come into the dining room through the kitchen. She’d put on a long cotton robe over her amber-colored negligee, but it hung slightly open. In the soft light, she seemed to be nude beneath the cover-up.

“Hey, Ben,” she said breezily.

“So, I’m here,” he said. His eyes quickly scanned her body.

“Good. We’re glad,” she told him, touching his arm. Then she reached up and gently tweaked his earlobe. It’s her way of greeting people she’s fond of. Some find it annoying. Ben clearly didn’t mind.

Then, abruptly, she kissed him hard on the mouth. Could he taste the faint flavor of her pussy from the tongue-kiss I’d just given her? Theirs was a French kiss — long and deep. He held her in his arms for several moments.

My dick stirred again.

“So it’s happening, then, huh?” Ben said. He wasn’t at all timid. In fact, he was borderline cocky.

“It really is, Ben,” Delia assured him. “Here’s to special friends.”

The three of us clinked glasses.

“I love this,” Ben said. “But it’s fucking surreal.”

Surreal? Yes. But at that point, things were getting just plain real to me. Our hookup was no ordinary swinging encounter. I’d known this young man for years. He used to pal around with my son, Dave, when they were in college.

Back then, Benny was a chunky, full-tilt geek who would corner me and Bev — my son’s mom, who’s now my ex-wife — and talk on and on about how nobody understood the beauty of mathematics. Benny and Dave’s friendship hadn’t been a long one, and if Benny hadn’t been such a character, I probably would have forgotten him.

Much would change in my life in the years between then and now. Dave moved away, went to law school and married a lovely young woman.

Bev and I surprised everyone by divorcing amicably. We both felt it necessary. There were no hard feelings.

Then I met and married Della — a sexy, funny woman, 15 years my junior.

Different lives, and different sex lives, too. Della and I have been in the so-called lifestyle from the start of our relationship. We explore our sexuality with other people — sometimes together and sometimes apart. I discovered, too, that I have a penchant for hotwifing and more than a touch of cuckold curiosity.

Della’s fine with all this. She’s a dark-haired, petite, no-nonsense woman of 37 with a wicked smile, gorgeous breasts and a firm, rounded ass that gets many sidelong glances.

One day I was listening to a radio talk show featuring local authors. I was sitting there as this guy starts talking about his book, and within a minute, he was pitching the glories of studying and really understanding mathematics.

Yep, Benny. But the voice was much deeper, more assured. Later, I found his website, which was one big commercial for his book. The slim volume he’d written was meant to explain brain-torturing mathematical concepts in an entertaining way.

And there was a video interview with him on the site — again, drumming up business for his book. He was definitely not the Benny of old. He may not have considered himself a bodybuilder, but he had definitely spent some time in a gym. More than that, his whole demeanor had changed. He was confident, friendly, optimistic and still smart as hell.

When I showed the video to Della, she all but drooled.

“I want him!” she said.

I tried to explain to her: No, he was my kid’s friend. It was too weird.

But we reached out to him online and congratulated him on the book. He was glad to hear from me. The three of us met up in person. There were hardly any vestiges of the old dweeby Benny. He was some kind of alpha male.

Suddenly, I had a change of heart.

“I’d love to see him go to town on your pussy,” I told Della afterward.

“Yeah, but you think it’s too weird,” she pouted.

“Maybe. Maybe not.”

We extended another invitation to Ben, and he took us up on it.

That night, he pulled me aside during his visit to say, “So, you and Della. You’re swingers, right?”

I stammered and sputtered. But I finally admitted that we were.

“Got that vibe from you from the start,” he said. “Believe me, I’m no stranger to the scene.” He paused. “Hotwifing, am I right?”

My face reddened.

Things moved pretty fast after that. Ben and Della’s flirtations got more intense. And then, there we were — in our big master bedroom, surrounded by a dozen candles with flames flickering like little tongues. Ben and Della sat at the foot of the bed, while I watched from a nearby chair.

Ben pushed my wife back on the bed and kissed her, his muscular body draping over her delicate, almost birdlike one. His dark features went well with hers. I was the odd man out: fair and freckled with graying blond hair. When they finally ended their kiss, she said, “Do what you want with me, Ben. But not too gentle. Make it so I won’t forget it.”

“Not much chance of any of us forgetting this,” he said.

Ben got up and pulled down the quilted coverlet. Della had already removed her light robe. She went to him, and he kissed her hard and fast once more. Then he gingerly removed her gauzy negligee, exposing her firm, rounded breasts with their dark, bullet-like nipples. He wasn’t so leisurely when it came to removal of her cotton panties. He pushed her down on the bed and yanked them off aggressively.

“Oh, cool!” he said. “A cute little hair pie. I like that. I’m all about the pie. Favorite dessert. Also, all-time favorite number.”

“Oh, you mean pi?” Delia responded.

“It goes on forever. After the decimal point — after the period.” He felt her pussy. “And it seems we don’t have to worry about any periods today.” He laughed.

Christ, a smutty “pi” joke? Ben never failed to work mathematics into the conversation — even during his pillow talk. He positioned his face between Della’s legs and let his tongue play where mine had been before.

Della moaned the way she moans when she gearing up for a great orgasm. She squirmed as he lapped at her clitoris and labia.

By that point, my cock was fully erect. I pulled my sweatpants to the floor and began playing with my dick. There were already a few drops of pre-come oozing from the tip.

Although Ben seemed to be in deep communion with Della’s pussy, he hadn’t forgotten me.

“How are we doing, Robert?” he asked.

I hadn’t expected him to address me, but I got over my shock and said, “Looks like you’re doing great.”

“Tell me how I should take her over the edge.”

I didn’t have to think twice.

“Suck her clit,” I told him. “Suck it hard.”

“Got it.”

And he went right for her magic bean. This went on for a minute or two, with Della’s moans growing increasingly frenzied. Then some guttural humming sounds came from Ben’s throat, and somehow, that brought her to her first screaming orgasm of the evening. (There would be three more before all was said and done.) Afterward, he kissed her softly, soothing her.

“I could do this all night,” he told her.

“Please do,” she answered. “Will you take your clothes off, Ben? I want to see your body. I want to see your...”

“Cock?

“Yeah.”

He stripped to the buff. His body was hairy, and his arms, legs and chest were thick. So was his excited, tusk-like penis.

Delia was on that thing in a flash. She had him in her mouth and was sucking on it with the same vigor Ben had used on her love button. My God, she was even trying to deep-throat the thing, which had to be a good eight inches. He knelt there on the mattress, arms akimbo, as she gave it her best effort.

“Damn, that’s good,” he told her as he ran his fingers through her hair. Then, calling over to me, he said, “Your wife can really suck a dick, Rob.”

I was stroking myself in earnest.

After a minute, he asked her, “Can I fuck you, baby?”

“Yes.”

“How?”

“Missionary.”

She lay back as he took a condom from the nightstand and strapped it onto his boner. He plunged his cock into her cunt and began pumping, all the while talking a dirty streak to the two of us, including such gems as: “Let me fuck you harder, Della,” and, “Oh, she’s so wet for me, Rob.”

He practically shouted when he shot off inside her.

Smiling, he got off the bed. He pulled the condom off his dick and brought it over to me, showing me the big, goopy load that it held.

“Here’s a souvenir for you.” He handed the used rubber to me. There was something a bit crazy in his eyes. I held the jizz-filled prophylactic in one hand as I stroked off a hot load with my other — shooting cream all over my belly.

“That’s a good cuck,” he said.

Della laughed delightedly.

Then our young friend went back to the bed for his next round with my beautiful wife.

“There’s more?” I asked.

He wrapped a sweaty arm around her as he played idly with her tits.

“You do the math,” he said.