A witch card-player, Archangel Gabriel and frankly terrifying Supernatural fan convention later, and Team Free Will had a clue to go on.

'Bela didn't give the Colt to Lilith,' said Sam. 'She gave it to a Demon named Crowley.'

Callisto choked on the tea she was drinking.

'Crowley?'

Castiel turned to her.

'You know him?'

'Yeah. We don't get on,' she said, shortly.

'How?' asked Dean, suspiciously.

'He, uh, helped us out a bit with the last apocalypse. Common interests, and all that. He and Aziraphale have been…close…for a while.'

Dean snorted. Sam raised his eyebrows but said nothing. Castiel merely said,

'I will find him.' And disappeared.

A couple of minutes later, Dean's phone rang. He picked it up.

The Demon Crowley is making a deal. Even as we speak, it's…going...down.

Callisto snorted and leaned back against the Impala's hood.

'Going down?' Dean looked incredulous. 'Ok, huggy bear, just don't lose him.'

I won't lose him. There was a pause. I followed him. It's not far, but…It's layered in Enochian warding magic…I can't get in.

'That's okay,' said Dean. 'You did great, we'll take it from here.'

He hung up and turned to the others.

'We've got a hit on Crowley. Let's go.'

They pulled up a few meters away from the gate.

'This plan is ridiculous,' said Callisto, for the umpteenth time.

'Don't be silly, no one can resist a damsel in distress,' said Dean, clicking his tongue and winking. Callisto rolled her eyes and got out of the car, tugging at the hem of her minidress. She walked up to the gate and pressed the intercom.

'Hello? My car broke down, I need some help.'

'Stay there, we'll be down in a minute.'

A couple of seconds later, the gate opened with a metallic squeak. With a look over her shoulder, Callisto began to walk up the driveway. Two men in suits came down to meet her.

'Evening, pretty lady,' said one. 'Why don't you get yourself on in here?'

Callisto smiled.

'I just need to make a call,' she said, coyly.

'You don't need to call anyone, baby,' said the man. 'We're the only help you're ever gonna need.'

'You know what? I think I'll just wait by my car, actually.' She turned to walk away but the man's hand came down on her shoulder.

'We said, get your ass in here.'

What happened next happened very fast. Callisto grabbed the man's wrist and turned around, twisting his arm behind his back. With her other hand, she pulled a knife out of her bra band and plunged it into his neck. Without hesitating, she wrenched the knife out and threw it at the other man. It buried itself in his chest.

Within seconds, both Demons were lying dead on the ground.

Sam and Dean came up behind her.

'Where did you learn to-'

'The government,' said Callisto, walking briskly up the driveway. 'Long story.'

They stole into the house through the back door. Sam drew a hasty devil's trap under one of the rugs while Callisto cut the power. They didn't have to wait long before they heard footsteps coming down the hall.

'It's Crowley, right?' asked Sam. The Demon came to a standstill just before the Chosen Rug.

'So, the Hardy boys finally found me,' he said, sounding unimpressed. 'Took you long enough.'

He paused, catching sight of the rumpled rug. He bent down and turned over the corner, then looked up.

'Do you have any idea,' he said, 'how much this rug costs?'

'Probably about the same as that vase you shattered, so I'd say we're even,' said Callisto, stepping forward. She didn't get far. Three Demons seized them from behind. Sam and Dean struggled, but Callisto stayed perfectly still and rolled her eyes.

'Callisto,' Crowley smiled. 'Lovely to see you.'

'Crowley. Always a pleasure.'

'How long's it been? What, fifteen years?'

'About that, yeah.'

'So how did you end up with Tweedledum and Tweedledumber?' He inclined his head towards Dean.

'Long story short, Maximilian Summer's out for my blood.'

Crowley winced.

'I don't envy you, love.' He clapped his hands. 'To business. This is it?' He picked up the Colt. 'This is what it's all about.'

Crowley swung his arm up, pointing the gun at Dean's head. He thumbed back the hammer. Then, he moved his arm three inches to the left and fired. The bullet hit the Demon holding Dean. Crowley fired twice more, killing the other two Demons. They stared at him.

'We need to talk,' he said. 'Privately.'

He led them into his study and shut the door. Sam and Callisto exchanged baffled looks as they walked down the corridor.

'Ok, what the hell is this?' asked Dean. Crowley sighed patiently.

'I forget that you two are, at best, functioning morons.'

'You're functioning…morons…' responded Dean, in that sharp and clever way that only he knew how. Crowley ignored him.

'I want you to take this and empty it into Lucifer's face.'

'Oh, my God,' groaned Callisto. 'Is he still butthurt over the whole averting the apocalypse thing?'

'Just a little. Lucifer's not my greatest fan at the moment.' He turned back to Sam and Dean. 'Lucifer isn't a Demon, remember? He's an Angel. An Angel famous for his hatred of humankind. He sees you as…filthy bags of pus-'

'Charming,' muttered Callisto.

'-and if he sees humans like that, what must he think of us?'

'But he created you,' said Sam. Crowley shrugged.

'To him we're…servants. Cannon fodder. If Lucifer manages to exterminate humankind…We're next. So, what do you say? How about I give you this-' he held out the Colt, '-and you go kill the Devil for me, huh?'

There was a silent pause. Crowley wiggled the gun encouragingly, a winning smile on his face. Sam reached out slowly and took it.

'Ok,' he said.

'Great,' beamed Crowley.

'You, uh...Wouldn't happen to know where the devil is, by any chance, would you?'

'Thursday. A little birdie told me he has an appointment in Carthage, Missouri.'

'Great. Thanks.'

He raised the gun to Crowley's head and pulled the trigger. Nothing happened. There was an awkward pause.

'Oh yeah, right, you probably need some ammunition.' Crowley went over to his desk and rifled through his drawers.

'Um, if you don't mind me asking, aren't you signing your own death warrant?' asked Dean. 'I mean, what if we go up against Lucifer and lose?'

'One - he's going to wipe us all out anyway. Two - the minute you three leave, I'm going on an extended vacation, all points nowhere, and three - HOW ABOUT YOU DON'T MISS. MORONS.'

He tossed the pack of ammunition to Callisto, who caught it.

'In fact,' said Crowley. 'How about you just let Azrael over there take care of it? If you want a job done right, ask a government-trained assassin.'

Dean turned to Callisto.

'You're an assassin?'

Callisto gave Crowley a look.

'Spill all my secrets, why don't you, mate?' She turned to Dean. 'Used to be. Again, long story. Let's go. Crowley, I would say it's been a pleasure but, let's face it, I don't understand how Aziraphale's tolerated you for six thousand years.'

'Likewise, Azrael. Likewise. Now get the bloody hell out of my house, all three of you.'

The three of them went back to Bobby's, where Jo and Ellen were waiting. Callisto, having acquired an iPhone (albeit a 3GS - she would never forgive Carlel for sending her back in time four years), called Castiel, and he appeared a minute later.

Santana's 'Oye como va' was playing in the background and Sam and Dean were researching in the next room.

'So tell me again,' said Ellen, as she poured out shots of whiskey. 'Where did you come from?'

'Alternate reality London, 2013. Different world, same Angels and Demons.'

'Dean tells me you were a government assassin,' said Jo. Callisto choked on her tea.

'Oh for God's sake. When did he have time to tell you that?'

'I think you were in the bathroom.'

'You were a government assassin?' asked Castiel. Callisto rolled her eyes and put her mug down.

'For a bit. Yes. I was a government assassin. Let's get over this, shall we?'

'Quit hounding the girl,' said Ellen. 'I wanna see Angel-boy drink.'

Callisto clapped her hands together, grinning.

'Yessss.' She pushed six shot glasses in front of Castiel. 'Let's do this.'

'Three…' counted Jo. 'Two…One…Go.'

Castiel calmly downed the six shots, one after the other. When he was finished, he paused, then said,

'I think I'm starting to feel something.'

Jo snorted. Callisto laughed. Callisto had a nice laugh, Castiel noticed. It was something about the way her eyes crinkled at the corners. It made him want to make her laugh more.

'Callisto, your turn!' said Jo, pushing shots towards her. 'You have your regeneration thing. Enough with this tea thing.'

'Alright,' she said, grinning. 'I could drink the lot of you under the table anyway.'

And with a wink at Cas, she downed the shots in quick succession to cheers from Ellen and Jo.

'My fingertips,' Callisto held up a hand, wiggling them. 'They're tingling.'

'So does that make Castiel Gimli, or…' Jo laughed as she got up to get a beer from the fridge.

'I'd make an amazing elf!' Callisto called after her. Castiel just looked puzzled.

'Oh honey, you have a lot of pop culture to catch up on,' said Ellen, standing up. 'Callisto can start you off, I'm gonna go talk to Bobby.'

Callisto slid into Ellen's seat to sit opposite Cas.

'So that was from a movie called Lord of the Rings, based on the greatest books ever written,' she explained. Castiel listened with rapt attention. 'Four Hobbits, two Men, an Elf, a Dwarf and a Wizard. Their mission? Deliver the One Ring to Mordor and cast it into the fires of Mount Doom. We'll have to watch it sometime.'

At that point, Bobby's voice called from the study.

'Everybody, get in here! It's time for the lineup.' They came in to see him setting up an ancient Pentax. 'Usual suspects in the corner.'

'Oh, come on, Bobby,' said Ellen. 'Nobody wants their picture taken.'

'Hear hear,' said Sam.

'Shut up,' growled Bobby. 'You're drinkin' my beer. Anyway, I'm gonna need somethin' to remember your sorry asses by.'

'Always good to have an optimist around,' Ellen commented as they grouped up. Callisto stood in front of Sam, arms around Ellen and Castiel. She was tall, but barely came up to Sam's chest.

'Bobby's right,' said Castiel. 'Tomorrow, we hunt the Devil. This is our last night on Earth.'

Callisto turned to glare at Cas, and at that point, the camera went off.

It was late, and everyone had gone to sleep. Callisto lay awake on the couch she'd been assigned, staring at the ceiling. Careful not to wake Dean, who was passed out on the adjacent couch, she got up and padded to the kitchen. She was just in the process of making herself a salami, ham and bacon sandwich when she heard a voice behind her.

'Can't sleep?'

She turned around; Castiel stood on the other side of the counter. Callisto shrugged.

'I was hungry.'

'Are you nervous about tomorrow?'

Callisto buttered the second slice of bread and placed it carefully atop her smoked meat mountain.

'For myself? No.' She put the plate and a mug of tea onto the counter and sat down opposite Castiel. 'I mean, what can Lucifer do to me?'

'Explode you into a million pieces,' said Cas, with a straight face. Callisto shrugged, taking a bite of her sandwich and chewing thoughtfully.

'I'd just put myself back together,' she said, finally. 'Nothing can kill me.'

'How do you know that?'

She paused, staring down at he plate. Then, she looked up at him.

'I've been…experimented on.'

'By whom?'

'Long story,' she said, taking a another bite.

'You always say that,' said Cas. 'But you never explain anything.'

Callisto swallowed.

'Some other time,' she said. 'What about you? Last time I checked, Heaven was one hundred per cent pro-apocalypse. So why are you helping prevent it?'

Castiel stared at her with those ridiculously blue eyes. Callisto matched his gaze, taking a gulp of her tea.

'I rebelled against Heaven,' he said, 'Because Sam and Dean showed me that I could. That I didn't have to do what others say without knowing why they're saying it.'

'You rebelled against Heaven?' She paused, mug halfway to her mouth again. 'That's hot.'

Cas didn't know how to respond to that, so instead contented himself with watching Callisto drink her tea. She raised an eyebrow at him.

'Do I have something on my face?'

'No.'

'Then why are you staring at me?'

'I don't know.'

'Awesome. You want some tea?'

'Yes, please.'

Callisto poured some into a mug and slid it over the counter, then checked her watch, an ancient, leather-strapped thing, made for a man.

'Two in the morning,' she muttered. 'We gotta be up in four hours.'

Castiel downed his tea in one gulp. Callisto winced.

'What?' he asked.

'You have to…You have to enjoy the tea,' she said, a pained expression on her face. 'You can't just knock it back like a shot.'

'I'm sorry. Have I offended you?'

Callisto laughed silently, her hand covering her mouth. She shook her head.

'No, you idiot. Here.' She poured him another mug. 'Slowly, yes? Savour the flavour.'

He looked at her and smiled. She grinned back.

'You don't dislike me anymore.'

Callisto shrugged.

'I'm not one to hold grudges.'

'You still dislike Crowley.'

'Yes, well, Crowley's never given me a reason not to. You're actually not too intolerable, once you get past the part where you shoved your hand into my chest the first time you met me.'

'I am sorry about that.'

'Apology accepted, halo-boy.' She rubbed her eyes.

'You're tired,' said Castiel. Callisto nodded.

'Really tired. But I can't sleep.'

'I could…I could help you. Put you to sleep until tomorrow morning, then wake you.'

Callisto bit her lip in an incredibly attractive way and frowned, thinking it over.

'Does it involve your hand entering my torso?'

'No. I tap you on the head.

'Oh. Ok then.'

They both stood and Castiel walked round the counter to her, his hand coming up.

'Hang on, let me get to my-'

But it was too late. Castiel's fingertips tapped her forehead and he caught her as she crumpled.