It was a steel sarcophagus of two inch thick steel, welded together over a number of days in the basement of their house. Just the right size to house an adult of either gender. They stood and admired it, having wanted some kind of lockable confined environment for as long as either could remember.
"Looks good Paul, what about the locking mechanism" asked Jen. "Oh, that's a work of genius." he replied. "There's no lock or key, it uses technology and chemistry to lock and unlock."
Jen looked puzzled, "Oh, what does that mean?".
Paul suggested she try out the sarcophagus and he would demonstrate. She went over to it and lay inside. Paul lowered the lid slowly and it made a loud bang when completely closed as it was so heavy. Paul had included a transparent toughened glass panel above the face area, so Jen was able to look out. There were a number of air holes around her head so she could hear Paul.
He explained "The glass panel you see through doubles as an advanced chemical scanner, specifically liquids. Any liquid is scanned, analysed and stored. To lock the device, add liquid, and that becomes the key. But to unlock it requires the same liquid again."
Paul thought a demonstration was in order.
Seeing his wife in the steel tomb got him hard, so he proceeded to masturbate over the situation and quite quickly reached a point of ejaculation, and he directed this onto the transparent glass above Jen's face. As he spurted his seed, the device scanned it, and a few moments later, a loud clunking sound could be heard, and the locks had engaged. Paul wiped the glass clean. "There we go. The key to you getting out of there is stored in my balls. To unlock and get you back out, I'll need to provide the exact same liquid again, it'll be scanned, and the tomb will unlock."
From within the tomb Jen said "Wow, that's amazing. Would any cum do it or is it down to the molecular level?" Paul explained it had to be the same liquid to work, and once unlocked, another liquid could be sampled, but only one liquid per locked session.
He quickly gained another erection and rubbed one out onto the glass in front of Jen and moments later he came, a much smaller amount this time. Seconds later, a loud clunk, and the lock disengaged.
Paul opened the lid and Jen climbed out. "Wow, what a kinky idea." she said. "Can I try it on you?" Paul nodded and climbed in. Jen lowered the lid with a thud, then dropped her skirt and panties revealing her bald shaven pussy.
She sat on the glass, Paul getting a perfect view of her pussy. She rubbed her clit and over the next few minutes got hornier and hornier. Eventually she was wet and oozing juices from her pussy, which she rubbed onto the glass plate. After a few more moments the sarcophagus locked with a clunk and moments later she came.
She stood up and pulled her panties and skirt back up, taking a tissue to clean the glass panel. She looked in on Paul and waved. He smiled back. "I guess your key is stored safely between my legs!"
She vanished for a while to let Paul stew, and he wondered where she'd gone. When she returned she asked how it was inside. "Relaxing but frustrating," he replied. Jen dropped her panties and rubbed her still moist pussy on the glass, causing it to unlock again. She lifted the lid and Paul got out.
They were both horny and turned on and fucked away on top of the steel tomb until Paul shot his load deep inside her.
They were wanting to play with their new toy some more, and Jen suggested Paul might like to go again. This time she insisted he go in completely naked, and she planned him to be in there overnight, so she suggested a diaper too. He climbed in, wearing his diaper, and had goosebumps from the feel of the cold steel. He laid down and Jen shut the lid.
She shuffled on the glass with her pussy and fingered herself to another orgasm. As she oozed onto the scanner the tomb locked. She cleaned her pussy up and wiped the glass clean and blew Paul a kiss, wishing him a good night's sleep.
Paul had a poor night's sleep, he was turned on and the inside wasn't very comfortable. He couldn't move much. He would pad it out better for next time. As the light in the basement increased as the sun came up, he saw Jen's beautiful face appear in his window.
"Did you have fun? Does my pussy prisoner want out?" he nodded. "Yes please, this prisoner needs to stretch!"
She was only wearing a night dress and rubbed her crotch, moaning to herself as she approached orgasm. She planted her pussy squarely on the scanner and Paul looked up at her beautiful ass and pussy from his confined space, its juicy emissions spread like snail trails across the glass.
As she came, and her sticky juices dribbled onto the glass, nothing happened. She smeared her pussy around on the glass, spreading it around but to no effect. She asked Paul what was wrong when he suddenly realised.
"Shit. Last night I came in your pussy and when you locked me in last night the liquid would have been a combination of your juices and my cum. After twelve hours your body will have absorbed or expelled anything I'd added". Jen added "I did have a shower before bed, too".
He looked panicked. "And I can't get you any of my cum as I'm trapped in here. I can't bend my arms to consider getting anything I can produce from my cock up to these air holes by my head".
Jen found the whole thing highly amusing. "So you mean to say you've inadvertently double locked yourself in with the only other key that can get you out?" He nodded. "Looks that way".
They never had protected sex as Jen was on the contraceptive pill, so there wouldn't even be any old condoms with his seed in.
"You did build in a failsafe, didn't you?" she asked. His panicked face gave her the answer she needed.
"I guess I'll need to put a feeding tube in there for now and hope you figure it out!"
With that, Jen went out of view leaving Paul to consider his predicament.
As it happened, Jen wasn't stupid, and she had considered this might happen, and had swabbed some of her mixed pussy juice into a small container last night.
Once he'd had the humiliation of thinking he was trapped forever more, and had to relieve and soil himself inside the steel tomb, trapped with his own excretions, she would let him free. But not before having several more orgasms right above his face, to see his hopeful then devastated face each time her climax and juices failed to free him.
She lost count, but it was about a week later when she decided to free him. By this time he was steeped in his own mess and looking a bit worse for wear.
She took the jar she'd kept and swabbed it onto her pussy lips. She then went to once again torture Paul who took no interest in her taunts after many failed attempts. This time her climax resulted in her smearing her combined juices onto the glass and with a clunk Paul was released.
She lifted the lid and Paul rubbed his eyes, sitting up in the tomb, looking disgustedly at his shit and piss stained body. "What happened?" he asked.
Jen told a lie and said she'd found her panties from the night they had sex and tried wearing them ahead of her latest attempt.
In truth, she loved the power she held over him. She told him not to be so careless next time.
Jen looked at the sarcophagus and imagined the fun she could have in there… the jeopardy they could play with… but it might be a while before she could convince Paul to try it again.
Having cleaned the sarcophagus she wondered if she could come up with new peril… maybe having her period on the scanner but Paul cutting a hole near her crotch so he could sample her excretions to let her out. She would be locked in by her own menstrual cycle… she could take oral contraceptives and mess with her cycle not knowing when she might escape …
What if she could somehow unwittingly collect other samples that would be hard to reacquire… from friends or strangers… she felt this could be the start of some amazing games.
She rubbed herself to orgasm and waited for Paul to finish his shower so they could plot their next fun.