Basically this whole thing came from a personal headcanon of mine about Darling. I know from personal experience that twitches don't come from nothing. This is set a short time before Captain Cook, ad It's almost definitely nowhere near canon, but I like it...
It was morning in the trenches, and already there were smatterings of gunfire from somewhere to the left of their trench. Blackadder was taking the chance to put his feet up, before the new day of madness truly began. It was their turn on patrol in an hour and the weather wasn't looking promising.
"Another storms on the way Captain," Baldrick as he came through the door.
"Well that's just great," Blackadder sighed. "Twelve hours standing in the rain, followed by twelve hours lying in the mud," He took a large gulp of water from his canteen. He'd initially drunk coffee or tea, but since learning of Baldrick's rather...creative Ersatz ingredients, he'd decided to stick to water. At least he knew which puddle it came from.
The phone on the desk rang and Blackadder sighed and picked it up. "Yes? Oh hello, Darling...oh yes?" He sighed. "Okay, if I must. I'll be there shortly." He put the phone down and turned to George and Baldrick. "Right, that was a call from HQ. Apparently Melchett has another plan for our unit."
"Oh why can't they call on someone else for a change? Whenever there's a new danger it's always us that has to do it!"
"I don't know; probably Darling hedging is bets trying to get us out of his hair."
"Captain Darling's always such a poor sport," George sighed. "I often wonder who spat in his coffee to put him in such a foul mood."
"That was probably me, sir," Baldrick admitted. "That reminds me, do you want a cup?"
"Ah go on then, Balders."
Blackadder considered for a moment as Baldrick handed George the cup of unmentionables.
"Funnily enough, I used to know Darling before the war actually," Blackadder noted.
"Really?" George asked in surprised.
"Oh yes, we grew up in the same town. Knew each other through school. Always been a natural pencil pusher, that one. Lost contact with him when I joined the army and didn't see him again until he turned up to nick the job as Melchett's secretary from right under my nose. Probably a blessing in hindsight, but he's still a smug bastard about it even now."
"That's interesting, sir. You know I've always wondered about his," George spasmed his eye in a badly mimicked twitch.
"I honestly don't know," Blackadder mused. "Didn't have it when I knew him. Probably stress from having to deal with Melchett, and I wouldn't blame him. I can barely stand him for five minutes, let alone be in his office 24/7."
Darling was pencilling in the newest paper clip count into the office inventory when Blackadder and co. entered.
"What does the General want with us now, Darling?" Blackadder asked.
Darling twitched at the name, as per usual, and was about to make some biting reply when the door to the generals office slammed open
"DARLING!"
"Sir!" Darling leapt to his feet, nearly snapping his pencil in two.
"Ah, Blackadder!" Melchett spotted the captain. "Glad you and your boys could make it!"
"Wouldn't miss it for the world sir!" George said eagerly.
"And I'm rather sorry to miss the world for this," Blackadder muttered, earning a sharp glare from Darling.
"Why have you called us in this time, sir?" Blackadder asked louder.
"I got word this morning that our fine soldiers have reclaimed some of our trenches back from Jerry's forces. I want you and your boys to accompany us down to the trenches to see the state they were left in. Apparently, they haven't been touched and were just behind the enemy lines when they advanced, but you never know what those Germans might have gotten up to there."
Rather than his usual sycophantic smug smile, Darling looked perplexed.
"Pardon me, General but which trenches are these?" he asked.
"The one six miles west along the front lines. Went behind the enemy lines two years ago."
Darling noticeably paled but swallowed it down quickly and bit out:
"P-pardon sir but if I may object, I-"
"No you may not! Honestly, Darling what's the matter with you?" Melchett scolded him.
"I'm sorry sir," Darling scrambled to recover. "But-"
"Just get the car ready, we're heading down there in an hour," Melchett took off out the door, leaving Darling staring desperately after him.
They reached the trench near dusk. It was a mess of broken ladders and churned mud, a few weeds sprouting along the base of the trench wall.
Soldiers had been there all day, digging out a couple of collapsed dugouts and setting up the basic equipment for the soldiers to be moved in over the next few days.
"Hm, not as bad as I thought. What do you think, Blackadder?"
"You'll be glad to know it looks like every other trench I've seen, sir."
"Sir-" Darling attempted to speak up again.
"Come on, Darling we need to inspect the finished dugouts." Melchett strode down the trench.
Blackadder frowned. Darling looked more on edge than usual, and he hadn't even been trying. Something was wrong.
As Melchett walked ahead, he sidled up to the beleaguered assistant.
"Are you alright, Darling?" he asked.
"Y-yes I'm fine," Darling twitched.
"Hm..."
"Carry on, Blackadder," Darling brushed him off, marching ahead woodenly after the General.
The trench was pretty horrific, but not really worse than any of the others. Someone had obviously attempted to fix up the dugouts, but it was still pretty bad.
"What's that stain there?" Baldrick asked, pointing to a dark patch on the wall.
"Probably some blood left over from when the trench was attacked," Melchett waved it off.
Blackadder noticed that Darling had gone pale at the sight, but assumed it was just him being squeamish.
"Well everything seems to be in order," Melchett clapped his hands together. As he did so, there was a loud crash of thunder nearly directly overhead them.
"Oh no," Blackadder sighed.
"Oh dear," George peered out of the door. "Looks like the storms caught up with us chaps."
"Well, it looks like you boys will be staying here tonight," Melchett told them.
"Wonderful." Blackadder said.
"Shall I call the car round, sir?" Darling asked.
"No, I can call them myself. You stay with them, Darling."
"W-what!?" Darling spluttered. "But we can't. This place is a mess, it isn't suitable-."
"No, don't let me get in the way of getting back down to basics, camping out in the trenches with the boys."
"But-"
"Now I'll hear no more about it. I'll see you tomorrow, Darling!" Melchett walked out the trench, calling out over the beginning patterings of rain.
"Don't look so gloomy, Captain!" George said to Darling. "It'll be fun!"
"I highly doubt that, Lieutenant," Blackadder said, unrolling his bedding on one of the bunks. The rain was now torrential outside, and they'd had to shove the door closed to stop the water diluting the dried mud inside the dugout. "I've been bunking with you and Baldrick for the past year and a half and it has been anything but fun."
"Just go to bed, Blackadder," Darling sighed wearily. He didn't have a bedroll, but there was basic sheets and pillow on the bunk to use. He missed his private room back at headquarters; sure it was the size of a cupboard, but at least he knew the bedbugs personally.
"Well I didn't realise it was possible to get into bed the wrong side, but you've seemed to have managed it."
He didn't know how long he's been asleep, but it was pitch black when Blackadder was ripped out of his dreams with a blood curdling scream, coming from the corner of the room.
"Wha-"
It took a few seconds to light the gas lamp, but when it finally glowed he saw where it'd come from.
"Darling?"
The captain was sat in the corner of the dugout, knees folded up to his chest and white as a sheet as he stared into the darkness. His twitch was going at a million miles an hour, jerking his head around so much it looked like he'd been possessed.
"What the-" Blackadder got out of his bed and made his way over to the other Captain.
"What is it, Captain?" Baldrick asked sleepily as Blackadder passed his bed.
"Nothing, Baldrick," Blackadder whispered. "Go back to sleep."
Baldrick didn't even reply, already dead to the world once again.
"Darling!" Blackadder snapped as he reached him. "Darling!" Where there was no response, he shook his shoulders. "Kevin! For god's sake snap out of it! What's going on?" Blackadder resorted back to the Captain's first name in hopes of pulling him back to the present.
Suddenly, Darling seemed to snap back to reality, noticing Blackadder and freezing, his breathing still laboured.
"Blackadder?" He frowned.
"Kevin what the hell's going on?"
Darling seemed to instantly seize up, going into his behind-the-desk look when he wanted to seem his most officious.
"None if your business, Blackadder, go back to sleep," he snapped, but his twitch gave him away.
"Captain, you just had a panic attack, I don't think that's nothing."
"Just go back to bed, Blackadder, that's an order," he snapped, lying back down onto his bunk.
"Darl-"
"Goodnight, Blackadder."
Seeing that Darling wasn't to be reasoned with, Blackadder sighed and went back to his bed. As he lay back down, just before he extinguished the lamp, he noticed that Darling had drawn his blanket up round his head.