From a prompt I received earlier this year on Tumblr:

The SSR/early SHIELD runs a training exercise with supermax prison cells, but then something else happens and the power goes out! Rose and Daniel on the outside, Jack and Peggy on the inside.

Sadly there is just a snippet so far. This is one I've been sitting on for awhile because I wanted to write the full version, but a piece will have to do (for now?). Tumblr crosspost is here.

--

"Any ideas?" Jack asked, looking up from the door of the cell after his attempts to use his penknife as a lock pick failed. He was grinning, and Peggy couldn't resist returning it. This kind of thing -- testing Howard's new high-tech prison cells -- was fun. It was a nice break from their regular daily routine. Hard to believe that a few years ago, she would've been horrified at the idea of being trapped in an extremely small prison cell with Jack Thompson.

"The lock is electric," Peggy said. "Perhaps we could short-circuit it with water from the toilet?"

"Nice try, but no," Howard's voice said over the intercom. "The lock is shielded. Water, bodily fluids, none of that will have an effect."

Peggy put her hands on her hips and looked up at the ceiling. "You thought of everything, didn't you? Daniel, are you there?"

"I'm here," Daniel said, with a soft laugh. "We can see everything you're doing in there, you know."

Jack held up a single finger to the cage-shielded camera in the corner. "Do you see this?"

"Loud and clear," Howard said cheerfully. "Great resolution on these cameras. They'll be out on the civilian market next year."

"How excellent for your bottom line," Peggy said, and that was the point when the cell plunged into darkness.

She stood still, shocked. Was this part of the test? The darkness was so utterly complete that it seemed to press on her eyes. "Howard?" she said. There was no answer.

"Did they do this on purpose?" Jack's voice came out of the darkness near her. "Hey, Sousa, if this is retaliation for offending your delicate eyeballs --"

"I don't think they did this." Peggy's voice sounded loud to her own ears. It was shockingly quiet. She could hear Jack breathing next to her, and it took her a moment to realize that the uncanny silence was not just because of the darkness, but because all the many ambient sounds of Howard's high-tech building had ceased. Most critically, from her point of view, the thrum of the ventilation equipment.

"Okay, this is fine," Jack said, his voice a little too loud. "This is peachy."

There was the small crack of a striking match, and a light flared in the darkness. Jack held it up, shedding its small light on the cell around them. It was bare-bones and simple, designed for temporary confinement of high-danger prisoners. There was a bed and a toilet, both bolted down, and that was it.

"It's possible the power failure might have released the lock," Peggy said. She gave the door a firm tug. Nothing happened. "Very well, perhaps not."

"So they'll be down to let us out soon, right?" Jack said. The match burned down to his fingers; he cursed and shook it out, plunging them back into darkness. "I mean, leaving us trapped in the dark wasn't really part of the plan."

"They might not be able to. All the locks in the building are electronic. If they don't release automatically, they might be impossible to open at all."

"Oh, well, that's great. Just great." There was a thump that she interpreted as Jack's fist striking the wall. "I knew it'd be a mistake to get Howard Stark involved with this. Knew it! And yet, here we are. They can't hear us, can they?"

"I don't think so," Peggy said. Regrettably so. She had a few things she wanted to say to Howard herself.