The truth of it is that Sammy doesn't need him anymore. His kisses haven't healed boo-boos since Sam was six and started first grade; his presence hasn't provided protection since Sam was fifteen and shot up six sudden inches. No, what Sam needs now is to forgive himself for making a target out of Jessica, and that'll only be possible when the Demon is dead.
The truth of it is that Dad doesn't need him anymore. After a campaign's over, the guys usually go their separate ways, and this one's nearly done. Dad loves the fight, but he gave it up once before, for fatherhood and suburbia. The Demon's death will act as Dad's second Honorable Discharge, and he'll be free to be the kind of father to Sam he's always meant to be.
It's okay. More than okay. He knows they love him.
Love and need aren't the same thing, not at all. They love him. They need to kill the Demon. He can do this.
The way he sees it, he's like duct tape. A workable solution for something broken, but a temporary fix at best. Dad got the three of them started on this quest, and he has a hunch Sam will be the one to finish it, but it's been up to him to get them here, to a place where they can all work together. It's been his responsibility to keep this family safe and whole, and judging from the way Dad had lounged and reminisced in the firelight at the steakhouse last night, the way Sammy's dimples had bought them a free round of pie and coffee from their waitress, he's succeeded.
The way he sees it, he's like a puzzle piece, surrounded by hundreds of shapes that mean Dad and hundreds that mean Sam. Lift him out of there, and the puzzle might not be complete, but the picture will still make sense.
He's been living on borrowed time since Roy LeGrange laid hands on him. He's just coming full circle now, death after life after death after life.
It's a straight trade, him for the Demon. More than that, it's strategically sound. He can do this.
He thinks of her. Every time he turns the pages of the journal, every time he steps between a monster and an innocent. He lives his life in her name.
He thinks of her. Whenever he sees his father's wedding ring, whenever Sam wears his crooked smile. He cherishes the people she loved most.
He knows he's only been a substitute for her, but he hopes intentions count for something, that she can see into his heart.
He'll know soon enough.
He nods as his father readies the dagger.
He smiles as the blade in Dad's hand slashes down.
He's done.