Sorry it took me so long. FF was being a butt. If you can't guess, the narrator here is Meg. (She was kind of awesome, actually, despite being a crazy evil demon.)
She thinks she could learn love from Sam Winchester's eyes.
She's watched him for a while now, observed from afar his interactions with the people around him. What they say is true: the Winchester bond could move mountains, start wars, fight every last creature of darkness on this planet and win. And she thinks that they could do it—together, they could beat Azazel, foil his master plan, topple destiny and overturn fate.
But divided they are weak. And so she will divide them.
The ties that bind them are the strongest she's ever seen. They're soulmates, the two brothers—she can smell it on them, the taint of love, and it disgusts her. It is an alien emotion, one she's not familiar with: she knows of hate, of anger, of sin, but the all-encompassing family is unthinkable. It's a potent word—with one use, all mistakes are absolved, all faults forgiven. Mercy is another concept she does not like. They orbit around each other, the Winchesters, like twin moons, and anger is melted away by the heat of two decades of shared history. Sam looks at his brother with eyes like suns, but she equates suns with fire; everything must be relearned with this new thing called love.
She is a demon. She knows how to corrupt, and Sam Winchester, for all of his efforts to be good, is easily corruptible. Dean is his rock, the post that supports him, but without his brother by his side Sam is weaker than he knows. She meets him first while he is alone, after he and his brother have parted ways and his loyalties are divided, and that is when he is hooked. He trusts her without thinking because without Dean he is a mass of contradictions—kind but prone to cruelty, trusting but suspicious by nature, innocent but guilty in the worst way. He is all light from the outside, but inside there is a dark, rotting core. His brother helps keep the darkness at bay, but they cannot always be at each other's side.
Right now, she is watching them. They don't know it, but she is—she's always there, the shadow in the corner of their eye. They are so attuned to the other that they orient themselves around each other like satellites. Dean moves, and Sam unconsciously shifts himself towards him; at the most minute change in Sam's posture, Dean will look up. Vigilance for his brother is second-nature to him.
She has no desire to love, but if she did, all she would ever know could be learned by studying the Winchesters.
His eyes, she thinks, are his weakest point. Sam's eyes are an illustration, a diagram of his feelings drawn out as clear as day. The eyes are the window to the soul. All his emotions are displayed on his face—she recognizes frustration, boredom, anger, sadness, as if there is a neon sign above his head proclaiming his feelings at all times. The littler expressions, the more subtle ones, are most often directed at Dean, or when Sam is lost in thought. Affection, empathy, nostalgia—and that fleeting, elusive one, the one seldom found in the Winchesters' eyes: happiness. It can be found most frequently when they look at each other, or when they are in the car they call home, or when they are repeating the most insignificant little traditions—bickering at gas stations or playing pranks on each other in cheap motel rooms. She will never understand humans. Their little quirks, all the bizarre things that somehow afford them joy.
She is most satisfied when she is hurting people, when they scream in agony and fear and she feels that rush of control, that thrill, the demonic equivalent of adrenaline coursing through her veins. She senses it sometimes in Sam—only a washed-out version, and only for the briefest of seconds, but every once in a while it is there, and when it is the emotion fear creeps into his all-too-expressive eyes. He is always without his brother on these occasions, always alone, with nothing to combat the darkness that hides within him. Sam Winchester is a time bomb, ticking and ticking and waiting to go off. One day the darkness will come out, spreading its oily fingers around his heart and his mind and those silly eyes and finally his brother, seeping into the person who is closest to him, and when it does that is when she knows he will break. She could almost feel akin to the boy called Sam, almost relate to that darkness hiding within him (only she has long made her peace with hers), except for one tiny problem—his brother.
Because when Dean is around it fades, when big brother is next to him and calling him Sammy and exercising his foul vocabulary the darkness recedes. She does not relate to him, no matter how much she could, because inside Sam Winchester there is also love of the highest degree—a light that leaks out in his laugh and his smile and in the way he looks as his brother, sinking into the darkness and obliterating it. She does not know Sam Winchester, because Sam Winchester loves.
And demons do not know love.