Tony hadn't slept.

Not "he hadn't slept well" like he'd had a nightmare or something. Though, he guessed he kind of had. He had a nightmare, only it wasn't in his head and his eyes had been open the whole damn time. This was a nightmare, and because of it, his head hadn't so much as touched a pillow all night.

Steve's, on the other hand, hadn't left one.

Since he'd passed out that night, Steve hadn't woken. Generally, it wouldn't have been that odd; Steve was one of the heaviest sleepers Tony had ever seen. Only, heavy sleeper or not, a guy tended to wake up when he was poked and prodded with needles regularly. Between the various blood samples they'd taken and the IV line Bruce had started to help with the dehydration and fever, they'd turned Steve into a regular pin cushion.

And he hadn't woken up. Not once.

Tony made up for it, though, with his insomnia. He'd had Clint and Jarvis help him set up a functional lab in his bedroom so he could be productive and not have to leave Steve's side. He and Bruce had both worked through the night, Bruce having taken over the lab in Tony's work shop, and they still hadn't figured it out.

They had gotten closer, though. The blood tests had helped: they'd found traces of an unknown metalloid element that Bruce was presently working to identify, along with high levels of beta-adrenergic blocking agents and potassium iodide.

At first, the last bit had seemed like an odd combination for a poison, but about an hour after they found it, Tony had figured it out. Beta Blockers slowed adrenaline and potassium iodide slowed thyroid production, which slowed metabolism. Adrenaline and metabolism: the two things ultimately responsible for Steve's super-strength and healing. This poison blocked those, and in combination with whatever the unknown element was in his bloodstream, it had left him unable to heal and too weak to fight off the toxin running rampant through his system.

There was no missing it: this poison had been tailor-made for Steve. A poison designed solely to kill Captain America.

Was it any wonder Tony couldn't sleep?

He felt better having something to do, though. Burying his head in the sand – sand here being a euphemism for work, scathing sarcasm, the bottom of a bottle, or d) all of the above – generally made him feel a little better. So, there he was, shoulders deep in figuring out a way to counter the Beta-Blockers and the potassium iodide while Bruce looked for the last piece of their poison puzzle.

Christ, now he knew things were bad: he was thinking in alliteration.

"Jarvis, brew another cup of coffee. Extra bold."

Because caffeine also made everything better.

"Sir, this is your eighth cup," Jarvis said in that voice that sometimes made Tony wonder how he'd made artificial intelligence capable of sass.

This was one of those times. "Just do it, Jarvis."

"Right away, sir."

Tony was just about to return to his work, had his hands poised on the touchpad and everything, when something stopped him.

"Is there anything I can do?"

Tony turned to see Thor standing in the doorway. There was a sad look on his face that made Tony's teeth clench. Why did he look so sad? Steve was going to be fine. There was no reason to look so god damned miserable.

"You can stop looking like someone drowned kitten, for one," Tony said, perhaps a little more sharply than he should have. Maybe all the coffee was putting him on edge. Either way, he took a deep breath and forced himself to at least try to play nice. "He'll be fine. I'm almost done on this end, as soon as I find something to stimulate his adrenal and thyroid glands to counteract the poison. I get his Energizer Bunny going again, he'll be back to his Star-Spangled self in no time."

Thor didn't even bother trying to sort through all the more technical points of what Tony had just said. Instead, he walked across the room over to Tony and put a massive hand on his shoulder. "He's not the only one I'm worried about, friend."

Part of Tony knew that Thor was just trying to be considerate, that he should be grateful. That he should accept his friend's concern and maybe even appreciate it.

But then there was the part of Tony that had spent the last seven hours standing vigil over his boyfriend as he lay sweating and groaning and grimacing, too weak and too sick to even wake up from whatever fever-dreams had him tossing like he was. The part that had poured over textbooks worth of biochemistry and medical journals until his eyeballs were ready to bleed. The part of Tony that had drunk eight cups of coffee and hadn't slept, and the part of Tony that was petrified that his boyfriend might just be—

"Alright, Arm & Hammer," Tony said. "Let's get this straight: whatever this is, this whole 'I'm here for you, bro' thing you're pulling, I don't need it. The only thing I need is for Steve to get his ass up off that bed and stop letting something as pathetic as this poison lay him out. So unless you can set that up for me, get out."

Thor made no move to do it, though. He'd stood through Tony's venting patiently, and when he was finished, he gave Tony's shoulder a firm squeeze. "Feel better?" he said, a sort of knowing half-smile on his face. He couldn't work a microscope, and he couldn't find a cure, but he had helped in his own way, and that pleased him.

Some of the tension eased from Tony's chest. "Little bit, yeah." He was just about to offer Thor some coffee – it was as close as he was going to get to a 'thank you', and he was probably about to overdose anyway – when he was cut short yet again. However, this time it wasn't a friend checking in.

This time, it was a cry.

It sounded startled, and it startled Tony and Thor both in turn so that they both whipped around to face the bed.

It had been Steve who cried out.

"Get them off me! Get them off!"

Tony was by Steve in an instant, one knee on the bed and his hands on Steve's shoulders, holding him still as his eyes scanned for the source of Steve's distress.

"What? Steve, what are they? What's on you?" Tony said. He sounded almost as frantic as Steve had. His boyfriend's panic had put him into a bit of a frenzy of his own; he had to make it better, had to keep him safe.

Mercifully, Steve seemed to be calming from the initial start. "Spiders," he said breathlessly, his fever-bright eyes searching the room as if he expected to see them crawling out at him and was confused when they didn't. "They were—I saw—"

"Shh," Tony said, slipping into the bed beside Steve and pulling him into his arms. He could feel Steve shaking, and he held him tighter, pulling the covers up around him and pressing a kiss to the top of his head. "You have a fever. You're hallucinating."

"But I—"

"There's nothing there. You're okay." He looked at Thor and nodded his head towards the sports bottle of Powerade on the bedside table. Thor took the hint, grabbed the bottle, and handed it to Tony.

Tony pulled the cap up with his teeth and lifted Steve's head a little. "Drink," he said, tipping the bottle to Steve's lips and holding it there until Steve had drunk a good swig of the blue liquid.

Thor was waiting to take it when Tony handed it to him. "Do you need anything else?"

"We're good," Tony said. "I've got him."

Nodding, Thor gave Steve one last glance and ducked out of the room, leaving Tony alone holding his boyfriend as tremors wracked his form.

"It's freezing."

"That's the fever. Just try to go to sleep."

Steve gave a shaky nod, but Tony noticed he leaned in a little closer, hugged Tony's arm a little tighter to his chest. "Hate being cold."

Tony guessed fifty years on ice could do that to a guy. He kept that remark to himself, though. "I know," he said instead.

Steve fell silent for a moment, but then, "Tony?"

"Yeah, babe?"

"Where was I hit?"

Tony's stomach twisted. "You didn't get hit," he said gently, trying to force back the rising nausea. He'd thought the hallucinations were over; he guessed the fog still hadn't quite lifted. "You got stabbed in the arm, but it's stitched up. It's not too bad."

"Huh…weird."

"Why? Why is that weird?" Tony was getting worried again, and he didn't like getting worried. Well, more worried than what had been his constant since Steve passed out. Steve's voice was reedy, like he was in pain or trying to hold back tears.

But Steve just shook his head and closed his eyes, his brows furrowing. He was hiding it, whatever it was.

"Steve."

Steve groaned. "'s nothing, just it—" Pause. Shift. Wince. Settle. "—it feels like it hurts everywhere but my arm." He forced a chuckle. "Weird, right?"

Weird wasn't the word Tony would've used. Worrying. Terrifying. Really, really, really bad. Judging by the way Steve kept stiffening and twitching, he was going to say the pain was from muscle cramps, but he couldn't be sure beyond that. Either way, it wasn't anything he could do right now. He wouldn't leave Steve alone like this, especially not while he was still awake.

So, he just held him, brushing his fingers through his hair. "Yeah," he said. "Weird. Now, no more talking. Just…just go to sleep." Because if Tony had thought watching him suffer in his sleep was bad, he'd had another thing coming once he could actually see the pain reflected in those gorgeous blue eyes.

Mercifully, Steve didn't fight him on it. Relaxing as much as his seizing muscles would allow, Steve let his head fall back on Tony's chest. He didn't close his eyes immediately, but Tony could see them fading out of focus as the seconds ticked on. It wouldn't take long.

Tony sat there in silence, holding his lover as the fog crept in again.