Alec Lightwood-Bane was pressed against a wall on the side of a bookshop in London with a seraph blade in his hand.
He had tracked a Greater Demon across the streets of London, where it had slammed the door to his Bentley rather gently (how one slammed a door gently was still a mystery to Alec.) and had leaned against the glass panes of the store, his sunglasses catching the moonlight and his posture relaxed.
No time to waste. He was the Inquisitor, and there would be a whole pile, maybe six, of work for him to do when he got back to Alicante. He had somehow convinced Jia, the Consul, that if he were to be the Inquisitor, he would need to work: both on the field and in the office. 
He slid out of the shadows easily, naming the seraph blade with a small whisper. Pressing it against the demon’s throat, he angled another seraph blade to slide under its rib. It had stopped him by holding a hand to the blade, disgust too human to be possible in its voice as it said, “You’re one of those Shadowhunter people, aren’t you?” Alec tried to shove the dagger again, using his weight and keeping the seraph blade against its throat stiff. The demon only pursed its lips, before shouting, “Angel! Come out, you bastard.”
There was no answer.
“Someone’s trying to kill me.” The demon tilted his head slightly toward the entrance of the bookshop, as if it wouldn’t die if it were to slit its throat on the blade accidentally. The door burst open, and someone stumbled out, wielding a sword that blazed with--
Heavenly fire? 
Alec was certain this was the strangest thing he had ever seen. London, on the other hand, continued milling about and going about their own business as if a man were not holding a sword that was flaming. 
The man cried out, “Let Crowley go!”
“Sir, I’m not certain you know what he is,” Alec reasoned. “He is dangerous, and very, very evil.”
Crowley grinned. “Hear that, angel? I’m evil.”
It was very bewildering for both the man and Alec, he presumed, but Alec realised that the demon had called the man an angel. So it was like that. Alec lowered the blades, and Crowley frowned, shaking the hand that held the blade. Blood splattered everywhere. The man hurried--the demon? Crowley?-- into the bookshop
“Alexander, darling, I’m sure you could’ve handled this better.” From another street, Magnus Lightwood-Bane emerged, all eyeliner and impeccable fashion taste.
“Yeah, well, you’re not the one that has to deal with a man in love with a demon, ” Alec huffed.
Magnus shrugged. The man had emerged again, poking his head through the door. “Please come in. Oh dear, I’m so sorry if I scared you.”
Alec and Magnus exchanged bemused looks. They were a warlock and a Shadowhunter. Few things could scare them when they were together.
When they entered the bookshop, Magnus started at the sight of the man, all limbs sticking in every direction on the couch. His sunglasses had been discarded, and he looked up at the sound of the door opening once more. The man had rushed to the back, presumably for bandages for the demon (Alec understood this, if not anything. He was full well Magnus could heal, but always bandaged him in the mundane way.) and Magnus knocked into a bookshelf. Alec steadied him, and followed his gaze to meet a pair of very golden, very slit, and very Magnus-like eyes.
“Asmodeus?” Magnus whispered. Alec instinctively grabbed onto his hands, rubbing their marriage ring in an attempt to calm him down.
“Do you not know your alphabet? My name starts with a ‘c’, not an ‘a’. C-row-ley. ”
The demon huffed, and Alec spotted a small, snake-like tattoo on the side of his face, just below his ear. “Snake eyes,” he whispered to Magnus, and tension leaked from the warlock’s shoulders.
“Terribly sorry, I’m sure Crowley here didn’t mean to frighten you--did you?” The man came out with a tray of tea and biscuits, with bandages tucked under his arm. He was wearing a white suit, which Alec found… strangely nice. Like he’d been wrapped in a blanket of happiness.
“I’m sorry, did you know he was a demon?” Alec gaped at Magnus’s bluntness, but they didn’t seem to be threatened as the man squeezed himself into the spot on the couch beside Crowley and begun bandaging him.
“Well, I have known him for a very long time, sir.” The man peered at the cut on Crowley’s hand, and all Alec and Magnus could do was watch, stunned, as the demon’s face softened.
As he caught the two of them staring, he scowled again. “Blast it, Aziraphale. Just tell ‘em who you are. Tall, dark and handsome over there’s a Shadowhunter. Made from… Raguel? Castiel? Some angel’s blood.”
Magnus snorted. Alec corrected him, saying, “Raziel.”
Aziraphale looked up, frowning. He snapped his fingers, and the bandages disappeared as quickly as they came. Alec stumbled backward and cursed, but Magnus caught him.
“What the hell?” Magnus frowned, the eyeliner on his dark eyes creasing slightly.
Aziraphale seemed to make himself bigger, “I’m Aziraphale, and I’m an angel.” He beamed at them. “Biscuits?”
Alec’s mouth hung open. “Angel. Like… a real angel. All wings and heavenly fire and all.”
Well, that explained the pet name.
Aziraphale shrugged. “Not sure about the heavenly fire part, but I do have a flaming sword!”
Crowley rolled his eyes. “Angel, demon, part-angel. What are you then, part-demon?” He gestured at Magnus, who stiffened. To others, it wasn’t as noticeable, but to Alec, he realised immediately. He put a hand on Magnus’s back.
“And you two are…” Aziraphale gestured vaguely to the hand on Magnus’s back.
“Married. Yes.” Magnus didn’t take his eyes off of Crowley. It was like watching a mouse glare at a thousand year old viper. When Crowley put his sunglasses back on, Magnus broke the stare. Alec chalked it up to him winning.
Speaking of eyes, Magnus had removed the glamour on his eyes, his cat eyes displayed in full glory. Aziraphale shifted, clearly as uncomfortable with the staring contest as Alec was, as a couch appeared on the opposite end of the bookshop, and Aziraphale smiled for them to sit.
Magnus looked cold, and Alec was reminded that though there were few things in the world that could scare them, an angel and a demon together were definitely on the list. He was stuck contemplating whether this man was truly an angel or if he were crazy and if Magnus was upset and needed a breather. He didn’t blame Magnus. It had been only a while back since Clary had come back, and their world was restored to normal. Sort of. Alec had undertook this mission, and Izzy handed the Institute over to her parabatai , Clary, for a brief while so she could accompany Alec and Magnus. Jace had expressed sincere apologies but had wished to stay with Clary--and Alec didn’t blame him.
“What brings you to London?” Aziraphale had a curious gleam in his eye Alec had seen in Izzy quite a lot when they were younger.
“Demons. Tracked him here,” Alec pointed at Crowley, “But he doesn’t seem to be it. The demons we’re hunting are Lesser Demons, but they’ve grown… smarter. Seem to have travelled here.”
After a long pause, Alec decided to solve his first question. He unsheathed a seraph blade, already spotting the shadow of a taloned hand outside the window. He named the blade ‘Aziraphale’, to Crowley’s amusement and Aziraphale’s glee.
And then he threw it. It ripped through the curtain and shattered the glass window, finding its mark into a demon, sticky black ichor staining the streets of London. 
 With his show of skills, and considerable ties to the Herondale, and possibly even the Branwell family, both powerhouses amongst the Shadowhunter families, Jia had given him two options: Go with at least one close family member, not limited to but preferably a Herondale. (She was likely talking about Jace, and Alec didn’t enjoy it. Alec without his parabatai would be a force to deal with, strengthened runes or not.) So he did. He originally had planned for Magnus, Izzy, Jace and Clary to come, but due to… Jace’s personal issues, Clary and Jace had took a raincheck. Jia allowed the trip, and contacted the London Institute beforehand. Lydia had been waiting, and they put their bags in their rooms before finding the largest demonic energy (Crowley) and attempting to wipe it out. (Also Crowley.)
 The last time Alec had seen heavenly fire was when Izzy had it in her body. It didn’t end up pretty, and he looked for ways to avoid it. Wrath of angels and all things considered, it was deadly. That flaming sword was probably deadlier than Glorious, and Alec wasn’t going to witness another bloodbath.
 London had also forgot, or left out the part that they'd almost been in an apocalypse with the world a while ago. There had been four eleven year-olds on bikes, a rather lovely lady with sharp eyes, an awkward man with absolutely no knack for computers, and two men dressed in black and white suits (Some swore they saw wings in the same shade of their respective suits) arriving. They had also conveniently left out the part where Lucifer Morningstar rose from the ground, or when they saw, quite literally, the Four Horsemen of the Apocalypse.
 Alec hadn’t actually been sure there was a demon outside.