Prompt: Sherlock comes home to 221B after faking his death. John and Lestrade had just been watching Dawn of the Dead, while drinking, so they think Sherlock is a zombie and keep trying to kill him. Again.
"If anybody could come back as a zombie," Lestrade said, waving his beer can at the screen in what he clearly thought was an explanatory manner, "If anybody could. You know."
"Sherlock," John agreed.
"Yeah," Lestrade said.
"It'd be for science," John said with an air of resignation, the same tone he'd use for heads in the fridge, hallucinogens in the sugar, flatmates coming back from the dead... "'Sorry John'," he made a passable attempt at mimicking Sherlock ability to speak at a speed just shy of holy fuck was that all one word, "'But of course I had to test the possibility of sustainable life past total brain death – why are you upset, is it because I made you watch me swan-dive off a building, I needed a trained medical professional to ensure there could be no questions about my deceased state, it was necessary – by the way I'm going to be keeping brains in the bathtub from now on.'"
He took a deep shuddering breath and watched the zombie on screen eat someone. "Fuck science."
"...I don't think science can consent to that kind of thing," Lestrade said.
"It would for Sherlock," John said. "The things he did to common sense, I wouldn't be surprised if he could make physics cry."
"Dunno, John, you're the doctor – do zombies come under the heading of physics?"
John thought about it. "Biochemistry and biophysics," he said firmly at last. "It was on a test."
Lestrade had one of those moments that happened less frequently with Sherlock gone, the sensation of the world slipping to one side with the acquisition of knowledge. "Christ, they test doctors on that sort of thing now?"
"No, it was a test I gave the lads in the squad. Afghanistan's the worst place to be turned into a zombie, the rate you'd decay."
And Sally was always so confused as to why John Watson would flatshare with Sherlock Holmes.
"So." Lestrade said after an awkward pause. Well. Awkward for him. John looked preoccupied with his staring match with the skull. "Zombie Sherlock."
"Yeah." John said. "I went – the first few days, you know – I went to the, the. Graveyard. Waiting for him to dig his way out. Had a shovel and everything, in case he needed help." His expression crumpled, like a mournful jumper-wearing wrinkly-faced puppy. "Only he didn't. He didn't want any help at all. Wanted to stay down there."
Lestrade thought about saying he was probably just distracted by the experience and study of decay, but was not quite drunk enough to risk another of John's crumple-faced expressions of woe. "S'okay," he said gently.
"s'not," John said miserably. "Typical Sherlock. No understanding of fucking universal laws except the one time it mattered. Then he decides to pay attention."
"Fuck him," Lestrade said loudly in an attempt at bolstering dismissiveness. "Er. ...you didn't, did you?"
"Still not gay," John said, with the resignation of someone who'd long grown used to everyone and their grandmother cooing over his relationship with his flatmate.
"Well, you've been kind of. Mourning period. Sad face. Victorian widow thing."
John stared at him. "What?"
"What?"
"No, what? Was that supposed to make sense?"
"I don't know, was it?" Lestrade said desperately. "I'm just saying. That's all. I can see Sherlock at the door." He blinked. One of those things didn't seem to match up to the rest. Wait. "I can see Sherlock. Standing in the doorway. That's not right."
"Fuck off," John said.
"No, seriously, zombie!"
John looked.
Sherlock looked back, hands held out in what was probably meant to be a placatory gesture and instead only hit every movie ingrained 'zombie! panic!' button in John's head.
"Gun!" John barked in such an authoritative tone Lestrade almost forgot the illegality of the request. He gave John a Look as he fought with the armchair to turn it into a blockade. The armchair must have taken advantage of his distraction, because it was winning.
"John–" Sherlock said urgently as Lestrade used the chair to shove him outside of the room before hastily slamming the door in his face.
"Not gun!" John corrected. "Harpoon!"
"What." Lestrade said, though he wasn't, strangely, really surprised.
"John–"
"There's one in here somewhere!"
"What."
"Knife knife knife," John chanted, lunging towards the fireplace and the yellowed papers impaled there. "No, fuck, that's short range..."
"John, this is getting out of hand now, I'm sorry, just let me in-"
"Oh god, we're going to die," Lestrade said, his back against the door, giving up wrestling with the armchair. "We are too drunk to defend ourselves against zombie attack. All that training at Hendon, wasted."
"Speak for yourself," John said, tripping over his own feet in his search for a suitable long-range weapon.
"Oh for – I am not a zombie!"
"And I bet he complains about our brains afterwards!"
John paused, halfway under the table. "Well, yeah," he said, one eyebrow making a drunken attempt to raise itself. "It's Sherlock."
"Your brains would be useless as nourishment anyway!"
"See?" Lestrade said, outraged.
"Zombies are not articulate, you imbecilic drunkards!"
"You would be the exception!" John bellowed back, grabbing a box full of papers and flinging it aside when he realised there was nothing in it that could be used for decapitation. "Chattiest bloody zombie in the history of ever-"
"I'm not dead! I never was! I faked it!"
In the middle of his makeshift barricade, Lestrade giggled, clearly unable to help himself while under the influence.
"...I really think I'd prefer you to be a zombie."
"I said I was sorry – it was to protect you – Moriarty –"
"Fuck Moriarty with a pointy stick!"
There was silence from the other side of the door.
"See, that's why people wonder about you," Lestrade announced. "Well no," he corrected himself, "If there's a tearful reunion in five minutes and you swoon like a Regency heroine and then forgive him everything because he's your bestest ever friend and it's only brains the bathtub and the occasional murder to keep him fed and sort of alive and that's worth some emotional torture, that's why people wonder."
There was an even longer stretch of silence.
"...Seriously, Greg, shut up."
"You are not helping, Lestrade."
"I'm calling it like I see it," Lestrade said with whatever passed for dignity in the drunk.
"And that is why you are a terrible detective, shut up!"
"You're a zombie, I'm not arguing with a fucking zombie!"
"Just – Open. The. Door."
"Go on, Greg," John nodded encouragingly, "I c'n hit him with this chair."
"...You do realise I can hear you...?"
Lestrade opened the door.
The attempt to hit Sherlock with the chair didn't quite work out, to put it mildly. John was drunk, Sherlock wasn't, and even mostly dead, he was smart enough to remember how to duck.
"This was not the sort of greeting I was expecting," he said.
John scowled up at him from his position on the floor.
"Yeah? What sort of greeting were you expecting?"
"I thought you might faint. I brought brandy, just in case. Now, check my pulse. Please don't make me get signed certification of my alive state from Mycroft."
The crumple-face of woe made its triumphant return. "It's okay, Sherlock, we can handle this, what's a few brains between friends? You can keep them in the bath, if you like."
Lestrade had once hit his head repeatedly against the nearest wall in preparation every time he saw Sherlock appear at a crime scene; the sight of Sherlock performing the same action was immensely gratifying.
"I. Am. Alive."
"That's what all the zombies would say if they could," John said.
From the look of frustration on his face, Lestrade rather thought Sherlock was wishing he'd stayed dead.