For the record, I'm flat-out rejecting season 9's sudden decision to classify reapers as a type of angel. They never were before and that was just a really stupid move. Reapers are reapers and angels are angels. End of discussion.

They start from the beginning. Neither of them was present when Dean took on the Mark of Cain, but they know enough about that day, and what's most important is why he did it. They spill everything, from Abaddon to Gadreel to Metatron, and at least for Castiel, it's like watching Dean crumple down from the good man he once was to the next monster they have to hunt all over again.

It falls to Castiel to recount to Eloise their most recent encounter with Dean, and he hates every second of it, few though they be. He breezes through it with the summary, "We tried to convince him to continue undergoing treatment. We were turned down."

He feels Sam's eyes on him, heavier than he can express. He forces himself to act like Sam's not present at all.

Eloise interjects before he can go on, "Was that when this," and she gestures broadly to Sam, referring to his general physical condition, "happened?" Her eyes strongly indicate she already knows, maybe even more than the information she's requesting.

Sam, of course, knows the answer to be yes, but he locks his gaze on Castiel, daring him to elaborate beyond that one simple word.

And all Castiel can say is "Yes."

He sees the tension leave Sam's shoulders, but not from relaxation.

Eloise nods, and motions for him to continue.

"We've been here since then," Castiel says simply. "Just recovering. Sam from his injuries, me from the ones I healed. And making calls. Like the one that brought you here."

"Does anyone else know what he is?" Eloise inquires. "Aside from you two and Crowley? And, of course, Cain?"

They both shake their heads. "No," says Sam, "at least assuming Crowley hasn't told any of his underlings. Which isn't quite what I'd call a safe assumption."

A few seconds' pause, and Castiel dares to say, "Time for you to tell us what you know."

Eloise looks at him for a long moment, and finally she nods. She takes a few more moments, no doubt casting her mind far, far back, and confirms this with her first words: "When the human population consisted only of Adam, Eve, Cain, and Abel, I was… so curious about them. Unspeakably so. I was the only reaper stationed on earth at the time, and I had never seen a human before them, much less reaped one.

"God never gave me express permission, but neither did he ever forbid me from… going down. And talking with them. And Cain, Cain I took a special interest in." A half-smile flickers and dies on her lips. "I'm not just Abel's reaper. I was also Cain's friend."

Castiel glances automatically at Sam, who also meets his gaze.

"I cannot express to you," Eloise continues, voice completely neutral but eyes far away, "the pain I went through when he sold his soul to protect his brother's. But it was nothing compared to the day his eyes went black." Her gaze returns to them then, her expression full of nothing at all. "I have existed since the dawn of man and nothing I have experienced since then has compared. He was a good man, when he was a man. But the change was immediate. The difference between him and Dean is of circumstance, and it is the reason I do not envy you one whit." Again she smiles, and the expression is free of any mirth. "There were no humans around then for him to kill."

Castiel's brow furrows immediately. "But the Mark demands blood. He would have had to kill, or he himself would have died."

Eloise shakes her head. "The Mark kills its bearer only to move him towards resurrection as a demon. Once this has happened, there is nothing more the Mark can do." She sighs softly. "As long as he was serving Lucifer, the Mark was satisfied. Besides, killing demons worked and works just as well. Even animals take some of the edge off."

"The way you describe the Mark seems to support the way I have come to think of it," Castiel says slowly. "In my eyes, he is not Dean Winchester with the influence of the Mark of Cain—he is the Mark of Cain with the memories of Dean Winchester."

"An interesting perspective, but one I would somewhat dispute," Eloise responds bluntly. "The Mark is a very evil influence, and it does have a will of its own, but it does not exist in its own right. What it does do, however, is unleash all the basest and darkest desires of the one who bears it by removing the proverbial dam. Even the most profoundly good man is cursed with original sin—the fault of Cain's parents. The Mark would strip him of any virtue that keeps that concupiscence in check, of any desire to be good.

"Perhaps it would help to compare him to other demons. Now, demons come into existence when a human soul has been tortured for so long that it is no longer recognizable as human, even by the person himself, or herself. A man becomes a demon when he forgets, irrevocably, what it is to be a man. He loses his morals that way; they just fade into oblivion and they're replaced by scar tissue. Dean's moral compass was ripped out of him. By the Mark. He doesn't care, but he still remembers what it is to care. To be good. It's fresh in his mind; it's just that he's been freed from the burden of a conscience."

Sam stares at her for a good long moment, shock written clear across his face, but there's a thoughtfulness behind it. "That would tear him apart," he whispers at length.

"Indeed," she says agreeably. "Eventually. Once he's been running from his erstwhile humanity for so long he has nothing left to distract himself. But this will not happen until you are long dead."

Sam's expression is almost catatonic—a ridiculous descriptor, Castiel knows, as he was just talking coherently, but it is the one that springs to his mind nonetheless. And suddenly his gaze snaps up towards their guest, his eyes growing large and taking on an almost manic glint, and he says, "He wants to get rid of us. That must mean we remind him of what he was."

"I will say this," Eloise says softly. "After Cain turned, it wasn't me he wanted to get away from. It was his parents."

Sam and Castiel, nearly in unison, blink, expressions blank.

"Angels and reapers are forces to be reckoned with," she goes on quietly, somberly, "but there is nothing quite like humanity. Imperfect, making frequent use of their free will which allows them to make mistakes, but always also feeling the drive to become something greater. Demons feel nothing of the kind. They know they cannot be anything greater. But such a sudden demon as the Mark creates—he still feels the echo, and it is strengthened in the mere presence of a human being. What he almost certainly is not aware of is that on an unconscious level, while he still remembers himself, he wants to feel this echo, he yearns for it, and it draws him to mingle with humans. But a human who knows what he used to be? The line is crossed. It is too much."

Castiel understands. Of course he does. He has always been aware of the cavernous gap between angels and men. But something inside him grows hollow at her words regardless. Perhaps the part of him that indeed once was human.

"What I am telling you, Sam," Eloise says, slowly and carefully, "is that you have the unique ability to inflict a world of pain on the thing that used to be your brother. If you were to appear to him a few hundred years down the road, it may help you win him back. Right now, he would kill you for it."

"Cut to the chase," Sam growls. "Is it enough?"

"To do what? To open him up to the idea of the cure, under any circumstances?"

Sam nods.

"No."

Castiel sags at the dull certainty in the word, but Sam snarls, striking the coffee table with more force than Castiel would have guessed him able to muster. "Then what the hell are you doing here?"

"I am giving you context," Eloise intones, unimpressed by his outburst. "It is rare to be able to foresee uses for such a thing. In the event that you can keep yourself safe, your mere presence will serve as a very effective distraction to him. And mainly? I am offering you my help. Am I correct in deducing that your plan is to find him, trap him, and cure him?"

"Yes," Castiel says.

"All distinct and challenging steps, but a reasonable solution. You are very fortunate to know of this cure." She gives the slightest of nods, considering them for a moment. "You have an ally in me. I will be looking for him. If I find him, or any trace of him, you will know immediately. If you find him, tell me, and I will have you standing next to him, or vice versa, before you can take another breath. I ask only for one thing in return."

Immediately Castiel is on high alert. But Sam asks before he can: "And what would that be?"

"We use the blood cure on Cain as well," she supplies swiftly, simply.

Castiel blinks, shocked, and is surprised when Sam replies readily, "Deal." He glances at Sam, his own eyes still wide. He's seen this expression on the man before. It is one of utter determination. And inherent to determination is hope. It's more hope than he's seen in Sam in quite some time.

And in turn, Eloise offers the closest thing to a genuine smile she's displayed thus far, and says, "I'll be in touch."

With that, she is gone.