Cas gripped the book hard and shut his eyes tight. He remembered the first time he had encountered Dean – that had been so very many years ago, but it all still shone bright in Castiel's memory. The recollection had become burned irrevocably into his mind. It had been approximately 4233 BC, though it was hard to pinpoint the dating exactly. It hurt Cas in an odd, familiar way to recall the very first encounter the two had had. Every time he thought back a new wave of nostalgia overcame him, and had he not kept a record of his times with Dean, he may have begun to forget some of the lives they had spent together. However, the first was one he would never forget. That first glance had been something indescribably beautiful. The book in his hands was Castiel's personal documentation of every life he'd shared with Dean, right back to the start.

It had been Cas' duty to come down to Earth back in what the humans called the stone age and assure all was in order. He glanced over several hundreds of tribes and colonies and never encountered much reason to stop (though, much to his shame come later years, it had been his heavenly law-abiding obligation to smite individuals and sometimes entire tribes who were deemed sinful or inadequate by the ever-unseen higher powers that had him in their unyielding control), yet during one sweep of the earth he had happened across a young man – a hunter, it looked like. He was one of those that would bring food back for the tribe, and he looked like a good one at that, but it wasn't this that Cas noticed first. It was the eyes. They snagged Cas and kept him where he was, caught wordless in their hold. Within those eyes he saw a world of wisdom, caring, loyalty... he saw something quite intricate and strikingly beautiful beneath Dean's tough exterior. Dean had not, of course, been called Dean back then – it was more of a rough grumble to ears of the modern people, though Cas understood it to be a rough grumble that roughly equated to Dean, if grumbles were to be equated to anything.

In his initial dazzled stupor Cas had failed to realize that the boy was hurt, which served as quite some shock when he finally broke out of the haze. A pang of something that was highly unfamiliar to Cas struck him – some form of worry or shock, he later supposed. The boy was pierced through by a sharp rock, which was speared through his abdominal region. He was trapped upon and in part beneath a pile of collapsed rocks, and the sight, however accustomed Cas was to beholding such scenes in his glances across the earth, had him feeling deeply unsettled and most importantly shot through with newfound fear. Dean was like an infant paddling in pools of his own blood, twitching and spasming in some failed attempt to release the hold on him. His beautiful face was rugged, his hair rough and skin scratched beyond belief. It went against every inch of his angelic instinct, but Cas felt inclined – obliged – to help the human boy. And fast. He could see the very soul slipping from the boy's form as his attempts at escape grew ever weaker.

And then the boy noticed Cas, his silent observer.

He ceased his struggle and tried to assume a dignified look, without realising he had nothing to prove to the angel that stood before him. So very hard he tried to appear as if he wasn't somewhat frantic, but his eyes gave all away. They were pleading, begging for release... but Cas knew that the human thought not of himself. He could sense it. No, the boy had a tribe that needed him... he needed to live for them. Surely there were children to feed, women.

It had been an intensely strange occasion. Within mere seconds Cas' whole world had changed, through the mere sight of a human, not unlike the others, but who stood out to Castiel as something different. For all the time the other angels had spent mocking Castiel, making him out to be beneath them, bullying him, Cas finally felt worthy in the presence of the human before him.

Cas could do nothing... all he could hope to do was attempt to pull the boy from the rocks and hope to god that his efforts at healing the boy manually would work.

Angels of his ranking were granted healing abilities, but only when the higher powers saw fit. The intense, stabbing realisation of knowing that at this point he had no guarantee of being able to save Dean had the angel just about ready to buckle at the knees. The boy had died that day, and it had been one of the most disturbing hours of Castiel's life. In just a blink of an eye relative to the size of his life so far, he'd made an unnatural connection with Dean, almost as if the two were soul mates... if the concept had existed, that is. Castiel had felt guilty for the death and replayed it over and over in his head, the way he had worked for over half an hour to save the boy before he eventually gave a last rasping breath and released the weight of his soul in his vessel's arms and how the angel had sat, holding the boy for yet another half hour afterwards, trying to understand the army of emotions he was battling internally and feeling very, very human.

The memory was painful, all of it. Cas had to stop. He had to stop thinking of that day. It was killing him, remembering that pain, feeling it again. But he couldn't tell Dean, he'd never tell him. He couldn't let the man he loved so much suffer under the weight of every life he'd never remember. Dean knew nothing of the angels, the magic they held. And who knew what would happen if Cas told him about all they'd been through? What would the angels do? What would Dean do?

Dean...

And suddenly a surge of desire flowed over Castiel, a surge that had never come upon him before but suddenly, for the first time in hundreds and hundreds of years, was overwhelming him.

Dean deserved to know, right? It was wrong to keep their history from him; their secret, perfect, painful history. God, Cas thought, why now? He'd never genuinely considered telling Dean all that had happened between them over the centuries, not seriously. In hindsight, it was strange that the urge to tell Dean of all the lives they'd lived out together, or of Cas' angelic status, had never been of much thought to Castiel, but that was the case nonetheless. He supposed that it was because pretending to be a human for Dean was nice and peaceful – a break from the stress of being an angel. Why was it that now the floodgates had opened and within minutes he was suddenly feeling the begging plea of a voice within him gnaw at his very soul, begging him to tell Dean about all of it? It was wrong and unfair and now Cas was feeling rather conflicted. It was almost as if his recollection of the past had brought about a parallel in the present, and he was yet again experiencing a very sudden and very alarming whirlpool of changes in his head.

Had Castiel been in any actual setting, and not in one of the many voids of heaven, he'd have been in some sort of nervous sweat and fidgeting liberally, but he was not. His internal clash was happening entirely within his mind. Maybe it was time to tell Dean. Maybe it'd be fine. Maybe... Cas couldn't. He was so far out of his comfort zone he could see the very illusion of comfort drifting off into the distance. It was like when he met Dean all over again. He couldn't tell him. He wouldn't. It was confirmed. Life would go on just as it had for the last several hundred years. Not another sudden change.

All the thought of Dean's coming into Castiel's life had Cas very much in mood to see him. Castiel wished the book in his hands gone, and it disappeared from sight. There was a flurry of wings, whose sound fell upon no ears in the void, and he was outside of Dean's apartment in New York, 1915. It was a murky place. The corridor walls were lined with stains of all natures and the floors were a horrible grey concrete. The smell of smoke lurked in every nook and cranny, along with a faint, but present nonetheless, aroma of faeces and urine. Cas would have loved to take Dean away, but for the moment that was not something that was possible. He braced himself and gave two short knocks on the dull brown door which stood before him, labelled '67' in worn bronze lettering. The door swung open in seconds to reveal a slightly dishevelled Dean. His face lit up clearly for a second or two, before he reined back his glee and attempted to appear casual.

'Cas! I wasn't expecting you...' His voice was immeasurably soothing.

'Hello, Dean.'

...that was what Castiel meant to say. What came out, however, was entirely unplanned; quite the opposite, really. Castiel had known deep down that change had never been something he could fight. And so, entirely against his conscious will, the angel said something that he knew would change Dean's current life forever, not ever hoping to realise that it would go on to affect his future lives too, as well as irreversibly damaging his own.

'Dean, we need to talk.'