There is a common plot device, often used to represent a hero being in the throes of a moral dilemma, which depicts a person (or a cartoon rabbit or duck or boa constrictor and so on) with an angel sitting on one shoulder and a demon on the other. One of these urges the person or anthropomorphized animal to do good, while the other tries to persuade them to do the wrong thing, whether this is eating a sinful ice cream cone or walloping the silly hunter over the head. The outcome depends on the sort of thing you happen to be watching or reading.
This is inaccurate.
Firstly, that’s not how it works. Angels and demons may have a vested interest in influencing the actions of mankind, and working on one soul at a time might be craftsmanship, but it’s very rare for them to put such effort into influencing a single decision. The free will thing is a bugger, and both heavenly and infernal parties find that setting up a temptation, or an opportunity to do good, and allowing human nature to run its course yields a better return on investment.
Also, while size is not an issue (being mostly a matter of physics, the laws of which do not bind those of fundamentally angelic stock) and balancing on a shoulder is doable with practice (budgies manage it, it can't be that hard), angels and demons simply wouldn’t be comfortable sitting next to each other. It would put them right off their game.
Crowley and Aziraphale would be an exception to this. They have known each other since the Beginning, and have, over the centuries, become accustomed to sitting together at restaurant tables, on park benches, in the interior of Crowley’s immaculate 1920s Bentley, and, back in the day, by the Gate of Eden, when there were fewer people and they all had a lot more free time. However, the Arrangement, which is part of the reason why they have gotten along so well for so long, means that they would never dream of working in direct opposition to each other. Aziraphale was an angel who took his job seriously and Crowley was a demon of his word: instead of the whole tedious business of shoulder sitting, they would have resolved the matter with a brief discussion about whose turn it was to report a success, made a note of it for next time, and gone off to have lunch a an interesting little restaurant where the proprietor knew them on sight. Much quicker.
John Watson didn’t know about any of this. He did know about the plot device, though, and if you asked him, he would have said that Sherlock Holmes, while ostensibly on the side of angels, sometimes had demons on both shoulders, egging each other on for the sheer bloody-minded Hell of it.
He would have said it affectionately too, although it have to be a growling, grumpy affection on mornings like this. Stumbling out of bed to find a half-dissected eyeball in the microwave, after learning there were no clean mugs and discovering a complete and total absence of milk, was not a good way to start the day. Particularly since he’d found out about the milk after he’d already made tea in the least crusty, most easily washed mug.
He had just resigned himself to the idea of pulling on some proper clothes and going downstairs to borrow milk from Mrs. Hudson when he heard movement in the front room.
Ah, he thought. Client.
And an Agitated Pacer too, by the sound of it. John was suddenly inclined be more forgiving about the state of the kitchen. The way people dropped in at all the hours God sent, you’d think 221B Baker Street was a hospital run by an especially dedicated species of nun.
He paused by the sliding doors, milk-less tea in hand, just in time to hear Sherlock say, “So what exactly do you want me to do about this?”
“Why, my dear boy, simply what you normally do,” said a clean, educated voice from the clients’ chair. Two of them, then. “Your services as advertised, so to speak.”
“I don’t advertise,” said Sherlock darkly.
“Then what do you call this - this blog of yours, pray?”
This was the point when either Sherlock needed a gentle but firm reminder to be polite, or the clients needed to be gently but firmly escorted to the door. John took that as his cue.
“Mostly he calls it rubbish,” he said, slipping into the room, mug-first. “And it’s my blog, actually. Hello.”
There were probably ways to look cool and suave while slipping into rooms dressed in your pyjamas. John suspected that a less tatty dressing gown would help, as would not having to shoulder your way through the sliding doors, but the main thing had to be not to look like you were dying for a cup of tea.
There were also probably worse rooms to show up like that in - somewhere in Parliament for a start, or maybe the Vatican - but the faces turning towards him had John wishing he could take his entrance back and have another go at it.
There was Sherlock, of course, polished and fully dressed (at this hour, a sure sign he’d been up the whole night) with his spine ramrod-straight in what John thought of as his no-you-can’t make-me-pose. And then there were the clients: the tall bloke with the good cheekbones caught in mid-stride by the window who was peering at John through designer sunglasses even though the interior of 221B was about as dim as a cave in the black mountains, and the one in the camelhair coat, who was holding his elbows in to avoid touching the clients’ chair any more than was strictly necessary. (John didn’t blame him - the last prospective client had smelled rather.) He was also, to John’s acute and bitter envy, holding a cup of tea from a tray that Mrs. Hudson must have brought up.
Both of these men were posh enough to give Sherlock a run for his money (a huge pile of it, with no small change). They were certainly posh enough to give John pause, but he was halfway through the doorway already, and he’d spoken to them, and, damn it all, it was his flat, so there.
And since it was his flat, he decided that he might as well help himself to some milk from the tea tray while he was at it. Mrs. Hudson was an angel.
The one in the chair blinked several times while he did this, then brightened considerably when things fell into place.
“Ah, Doctor Watson. Your blog, of course.” He smiled at John over his teacup. “Yes, I particularly enjoyed the one with the aluminum crutch. Great stuff.”
“Yeah,” chimed in the client by the window, sounding a shade less enthusiastic. “Great.”
He smiled at John too, a quick flash of teeth. If his heart had been in it, it would have been thoroughly unnerving.
“Oh. Well. Thank you.” John may have said this a little more warmly than the compliment actually warranted. This could be blamed on his having taken - finally! - his first, blessed sip of tea. He settled into his chair, taking up, as it were, his official position in the proceedings. “Thank you very much. And, um, what services did you need?”
Sherlock snorted. “The most pedestrian sort.” He waved a hand at two pieces of paper on the table beside him. In the best traditions of criminal letters everywhere, the text on them was completely made up of letters snipped from newspapers. There was the occasional whole word too, though John could see that the rather long name appearing on both of them had had each letter painstakingly cut out and pasted into place. They were longer than the average ransom note as well. It spoke of a special kind of resentment. “Anonymous threats. Detailed but unimaginative ones.”
“Of the most dire kind! Mister Holmes, the fate of the world--”
“Funny, isn’t it, how often that crops up?” said Sherlock, to John and only to John. As far as he was concerned, the interview was over and the fact that these two hadn’t left yet was merely a technicality. “The ‘fate of the world’ - it might well depend on my doing the dishes, given how commonplace it is.”
“Heaven forbid,” murmured John, thinking of the state of the sink. “The world’s done for, then. I think you two had better l--”
“All right,” the bloke in the sunglasses bristled, taking a step closer. It wasn’t precisely threatening, but he was wearing an expression, often seen on people dealing with Sherlock, that said he wanted to shake him. “How’s the end of the world for you? Would that be good enough, Mister High-and-Mighty Holmes?”
Sherlock let out a good, honest laugh at that. “You mean Armageddon?” he said, sarcasm sluicing from every syllable.
“Oh, no. No, no, no. Certainly not.” The client in the chair lowered his teacup. “The time for Armageddon has come and gone, and with the Antichrist living happily in Oxfordshire--”
“Until you bring up climate change,” muttered Sunglasses.
“--this is something of a more prosaic nature,” continued the first one, smoothly. “Merely the end of the world, without the Great War and all the implications thereof. Indeed, the world might continue for some time afterward - like in those films where they have those spikes on the cars - but it won’t do anyone any good.”
The way he said it made the hair on the back of John’s neck stand on end. It wasn’t just belief - anyone proclaiming Doomsday on the sidewalk could have buckets of simple belief. No, this man knew that what he was saying was true, so he was either for real or quite, quite mad. John wasn’t sure which option was more disturbing.
“And this is what brings you here?” Sherlock looked at them sharply, as if he was really paying attention this time. “Surely two supernatural beings would have better resources.”
John saved his spluttering rebuke. He figured the clients could do that, or get angry, or whatever it was people did when you said they were something other than human. What he did not expect was for the two of them to have nearly identical sheepish looks cross their faces like the Macedonian army crossing to Tyre, permanently altering the landscape.
“You’d be surprised,” said Crowley. He would never live down his embarrassment over the Witchfinder Army, and he was immortal. True, there had been five hundred and eighteen names on the payroll, but you didn’t need to read very far to get to Witchfinder Majors Saucepan, Tin, Milk, and Cupboard.
“The resources are there, of course,” said Aziraphale, sticking up for the old firm. “The problem is that they are, by necessity, polarized. My people cannot possibly work with his people, so we find ourselves in a bit of a quandary.”
“Plus there were - ah - complications with the actual Armageddon that might mean using those resources to save our own skins might be... let’s say ‘frowned upon’.”
“Prevented,” Crowley smiled thinly. “Maybe not officially, but they wouldn’t try too hard to stop anyone who was trying to stop us, if you see what I mean. Ever meet a Duke of Hell with a grudge?”
“I can’t say I have,” said John slowly. “Sorry, I - I think I’m missing something here. Did you just say a ‘Duke of Hell’? And ‘the actual Armageddon’?”
“He did, John, do keep up. It’s obvious if you look hard enough, though I will admit it took me a while to see it. An angel keeping company with a demon.” Sherlock gave his head a little shake, rebuking himself for being so slow. “That threw me off, but I got there in the end.”
Aziraphale beamed. “We thought you would.”
“Hoped, you mean,” said Crowley. “We couldn’t have come in saying, ‘Good morning, we’re just a couple of supernatural entities and we were wondering if you could help us prevent a knockoff of Armageddon’. It’s something you have to work up to in conversation.”
“I wish you had. It would have saved us all some time, and given John a chance to change out of his pyjamas.” Sherlock frowned. He was going to have to admit something painful. “Though now I understand what you’re doing here even less.”
“We need you to find the source of the notes,” said Aziraphale with careful patience, “as I was trying to tell you. We’ve tried on our own, but the signal is hopelessly muddled. Too much interference on too many levels.”
“Occult levels,” Crowley clarified. “See, they knew we’d look, right? Only natural for you to look when someone leaves something like that on your windshield--”
“Or your bookshop.”
“Or your bookshop, right. So they laid enough noise on the traces to give an archangel a migraine. It’ll melt any psychic’s brain in the bargain, so that option’s out. Good, old-fashioned detective work’s the only real choice we have, and they made sure we can’t take it to any of our usual agents by explicitly naming us both. So we’ve come to you, so you can do that thing where you look at the splodges of glue or the creases in the paper and know what kind of light was coming in through which window when they put it together.”
“To find a presumably supernatural entity or entities powerful enough to know about you two and hobble your abilities and bring about the end of the world,” said Sherlock bluntly. It sounded as though even he could see the problem with this, and he was never happy when clients made light of his deductions.
“Are you serious?” demanded John. This was a bit much first thing in the morning. He knew Sherlock was above staging elaborate practical jokes (the Fall, all right, and, oh God, Janine, but there’d been a point to those - messing with his head had been an unfortunate side effect), but he wouldn’t have been surprised to find that his tea had been drugged. Or his dinner, perhaps, and none of this had really happened and he was still in bed having a dream that was the result of his catching that rather terrible End of Days film on the telly before turning in.
“As a sheer heart attack,” said Crowley, stubbornly refusing to be relegated to the realm of John’s imagination. “We wouldn’t have come here together if we could’ve helped it.”
“And you just need to find them, mind you,” said Aziraphale. “Anything more than that would be much too dangerous for a human. An address will be enough - we’ll handle the rest.” His voice took on a cautiously hopeful note. “Can I assume you’ll be taking our case?’
“A chance to pit myself against the wits of Heaven and Hell?” Sherlock’s grin was the stuff of nightmares. It was the sort of thing that preceded John tackling him to the ground for his own good because he was taking advice from both the metaphorical demons on his Spencer Hart-clad shoulders. “How could I resist?”
Aziraphale all but clapped his exquisitely manicured hands. “Bless you, dear boy! Bless you!”
“Keep it down,” hissed Crowley. “And I wouldn’t get too excited if I were you. Heaven and Hell aren’t exactly what you would call ‘creative’. Intelligent, I’ll grant you, but you could probably outwit the average demon with your wits tied behind your back.”
“Except this demon, or other, has clearly been working on Earth - there’s nothing like the newsprint of the Daily Mail, see that ‘your’ and the ‘Z’ here?- having avoided detection from either of your authorities long enough to formulate a plan for an unauthorized apocalypse and, going by these notes, put it in motion. This is as good as having a second Christmas on Boxing Day.”
“And dangerous,” reiterated Aziraphale. He was looking slightly concerned, as a mad scientist might upon realizing a design flaw in his Great Work after he’s flipped the switch on an appropriately dark and stormy night. “You must be careful, Mister Holmes.”
“Always. I’ll have my best man with me, won’t I, John? John?”
John had been so distracted by all this that he hadn’t even noticed he’d finished his tea. His eyes went from the bottom of his mug to his flatmate then to the angel and the demon (he hadn’t sussed out who was which yet, but he was inclined to believe the worst of anyone who kept their sunglasses on indoors). They looked real enough, and the empty mug was solid and vestigially warm in his hands, just as it should be, but that wasn’t a guarantee of anything.
“Hang on a moment,” he said. “Pardon me for asking, but I just have to make sure: Is this real life?”