In the end, he realized he was an Old Testament man, maybe even a pagan. All that turn the other cheek, new convenant, prayers of forgiveness and salvation stuff hadn't meant a thing when it mattered. Instead, he found that the soul he once thought lived in his body instead lived in hers. She had held his own light, his own goodness, in trust for him. When she died, he was blackness and vengeance.
As he crept along the rafters, then stopped, and began waiting, he remembered. When the light in her eyes guttered out, his own soul's fire was extinguished, taking with it all thoughts of redemption. Not that he'd lived his own life by New Testament means most of the time. To a man with a gun, the old ways were easiest. Turn the other cheek yielded to an eye for an eye in the end. And when her light went out, he found that he believed now, along with her, that there was no God. If there was, He wouldn't have taken her from him. He hadn't listened to Booth's prayers to find her alive, to save her, to let her recover.
Instead, he only found her, bloodied and violated, alone after her tormentors already fled. There was too much blood for her to last much longer. He couldn't possibly move her without ending it sooner. But she knew him when he lay, eye to eye with her, her cooling blood on the floor soaking into not just his clothing but his skin, his being, the cold blood cooling him until he had the strength to do what would be required next.
"Booth," her lips said, as a touch of blood trickled out. She named her tormentors for him, and then gasped, another bubbling rivulet of blood leaving her mouth. "Coup de grace," she half-breathed, as he begged her to stay with him. "Better you than them..."
"No, Bones, I can't," he cried, knowing as she asked that he had no choice.
"Please," she begged. "Don't let them kill me. I want to die on my own terms."
He swallowed, and nodded, his lips meeting hers as tears ran from his eyes while he kissed her. Her blood coated his mouth as he gathered her to him, embracing her limp, broken form. "I love you," he whispered, then broke her neck. A smile turned her bloody lips up as she stared back at him until his soul went out with hers in her eyes. He killed himself when he killed her. The fact that he still breathed was a technicality. When she took her last breath, he shed his last tear. He carried her shell outside into the sunshine, the late-arriving swat team stopping in its tracks as they saw who he carried.
- - - -
He did everything required of him immediately after, including admitting to the coup de grace. Nobody blamed him, better that, from a friend, than alone at the end, they all thought. They didn't notice that he was dead, too. There was never enough evidence to get her two tormentors in the weeks that followed, so Booth made plans. He talked to a lawyer, put his finances in order, saw to her funeral, and caressed her waxen cheek one last time before walking away from the casket, leaving the services to those who hadn't already said the most intimate of goodbyes. The only time he visibly reacted to his partner's death was when he learned, after her funeral, that she'd provided for him and his son. Then he jerked once, as if kicked, before cold impassivity and planned calculation resettled around him again. The ones who didn't know him were surprised by his demeanor. The ones who did, and there were only three of them, only wished they could find their own way of making it through what was to come with some fraction of his determination.
Like some heathen ascetic, he cast off his worldly connections in secret, so those who didn't understand couldn't stop him until he was already gone. He'd internalized every injury dealt to her, made the squints tell him which weapons made which harm. None of them spoke of it outside the lab-- it was silent as a tomb, now, in her absence, and their gatherings were at night, off the official clock. His black implacability drove them to give them the answers he needed, even as he worked as tirelessly with them to piece together each fragmented clue. They knew, without asking, what he would do when all the answers were gathered.
That last morning, before he set out to finish it, he went to her office, right at pre-dawn, when she was often wont to start working. He'd come direct from his son's room, climbing in and out of the window to kiss him goodbye. There was a letter on his own dining room table that would tell Rebecca what she needed, including a letter to give to his son when he was older. Her office was the same-- the lab was in stasis. Only he had fully absorbed her loss as he swallowed her blood when he kissed her.
His black outer garments matched his inside. He wouldn't call what was left in him a heart-- his had stopped beating when hers did. He re-read the catalogue of horrors one last time, memorizing injury placement, depth and force of each mark, each violation, then closed it, setting it squarely on the sofa where they'd so often sat side by side, catching the bad guys. He laid his badge and standard issue weapon on top, along with the keys to his truck. The money she'd left him, the names that she'd given him, gave him and the squints her last bits of support, to bring them to this final conclusion. Even in death, she helped him in his work. This would be their last case together.
He wasn't surprised to see the three of the six they'd once been waiting, witnessing, when he straightened and turned, though he'd bid them goodbye only hours before. None of them questioned him as he shut off the light in her office, closed the door on his last links with the world, and faced them.
It was the least blasphemous thing he'd done, after breaking her neck, as he pressed a soft kiss of death on each of their foreheads, his cold fingers gentle on the sides of their faces, as he murmured a soft promise to each of them.
"An eye for an eye," he told Angela. "A tooth for a tooth," he promised Cam. "A life for a life," he vowed to Hodgins, and Hodgins opened his hand, the last weapon Booth hadn't found on his own held out for the taking.
"Redeemer of blood," Hodgins replied, pressing the cold, flat black weapon, sharp and deadly, into Booth's hand. He smiled at that last dark act of friendship, then turned to them all and said two last words. "Never forget."
He was gone before their own responding "Nevers" died on their lips.
- - - -
When her tormentors came, he captured them easily. He would almost think it was Providence, the way they fell to him, but he only believed in his own hands and brain now. There was no error because he'd left room for none.
He'd made Cam list out the order of injuries, patiently waiting each time she retched until she recovered, and continued ordaining the litany of death. He'd carved it in stone in his memory-- fifty six commandments in all, ending in the most important one. Thou shalt kill.
Solemnly, almost reverently, he declared each blow aloud before making it. Bones once said during one of her lovable lectures that the manner of a ritual could be as important as the result. She was right. He delivered her death back to them, except for the coup de grace he'd given her at the end. These two died as they'd meant her to die, their life breathed out in blood on the floor.
He left all the tools there except one he'd saved apart as he left them, repeating his now complete vows. "An eye for an eye, a tooth for a tooth. A life for a life, redeemer of blood." Passing outside into the night, he walked until he found a clear patch of sky, then lay down, eyes wide open. After searching, he found her favorite constellation, and wished on the star at the nose of the dolphin that he'd find her again. "I love you," he said, then closed his eyes and swallowed the metal death he'd dealt so often to others, choosing his death on his terms, as she'd chosen hers.
- - -
The three of the six remaining laid him to rest with her, as they'd know that they would when he first brought her back. The headstone was simple, bearing their names and their lifespans, beneath which were three simple words. Partners. Never Forget.