Fair warning: SPOILERS BELOW. This is an AU of the Season 7 finale. Read at your own risk. And for everyone else who proceeds... I'll just say... I'm sorry.

The Holtzman barn was creepy as hell. Shafts of light illuminated only so much of the cramped space, and the dust swirled by Castle's mere presence. Finding the car with the NYC sticker on the back, well, he had expected that, but the mask hanging there had certainly given him a fright, and the memories that had been resurfacing over the last few days struck him like the truck that killed Emma.

'You okay?'

Only the sound of Beckett's voice through the speakerphone brought him back to the present; to what he was doing. He needed to get a grip. "Yeah."

Finding the disturbed dust covered drawer, his curiosity drew him do it. He had no idea what he was going to find in there, but he hoped it was the evidence that would prove Beckett's faith in him wasn't misplaced. His heart thumped in his chest, adrenaline coursed through him as he slid it open and found a book. Curiosity drove him further.

More.

He needed more. He had the end of the story in his mind already-with Holtzman in handcuffs in the back of a squad car-but not knowing what happened in the middle... it was tormenting him. The answer was in this creepy rotted building somewhere, he knew it. He would find it.

Opening the book, he was momentarily stunned by what he saw, words and breath tripping over themselves to get out of his throat. All he managed was a breathy, "Oh god."

'Castle?' He kept flipping through the pages, and the guilt that had settled firmly in his gut earlier, it pulled at him even more at the sheer number of victims that he couldn't have helped. 'Castle, what do you see now?'

Dead faces with ritualistic markings carved into their skin looked back at him. Faces he'd see in his nightmares for years to come. "I see them. Photo's of his victims. I see all of them." He was transfixed by them. A running tally calculating in his brain while the weight of helplessness settled heavily on his shoulders. He knew now that he should have done more; that his eleven year old self should have done more than write down the truth he had seen and pass it off as fiction.

There was no apologizing for this.

The old doors to the barn slammed shut. Castle whipped around to aim his flashlight at it, and for a second, he thought it was probably just the wind, but that was classic horror movie stuff to get the audience riled up. This wasn't a horror movie. Just the wind? No… no. The writer knew that he had overplayed his hand. He challenged the psychologist in his office and Holtzman blinked, gave him insights he ought to have kept to himself. Castle knew Holtzman had been referring to himself, and Holtzman knew that Castle was onto him.

Uneasy, Castle looked around, and what he saw-or didn't see-made his stomach plummet. The mask was gone. The bastard was here.

Holtzman was trying to get rid of the evidence. "Beckett, he's here. He's inside," he whispered, frantically looking around for some sign.

"How did you find me?"

Startled, Castle kept searching, anxiety reaching untold heights. "I've been looking for you since Hollander's Woods."

"The boy... that was you." It wasn't a question, but a confirmation as the puzzle pieces came together to weave the tapestry of that day. It all made sense now. "I should have killed you when I had the chance."

Should have. It was sloppy to let him live, that's for sure. Even Castle knew how lucky he was. "You can't win, Holtzman. We know who you are."

"If doesn't matter. You'll both be dead, and they'll never find me."

Both. Beckett. Castle felt himself shaking, the monster inside him rearing its head to protect his wife at all costs. He wouldn't let that bastard get to her.

"Castle?!" Her worried voice came through the cracks of the wood, and she banged on the door with her fist, trying to get in, trying to help. As much as he wanted her away, he knew he needed her in this. He recognized his disadvantage, and if there was any hope of making it out on the other side, it would be with the woman who was armed. He just needed her. "It's locked!"

Castle ran for the door with the beam of wood cutting across it to keep it shut. He was close. The light at the end of the tunnel was just beyond those doors, but a force came at him from behind and tackled him to the dirt covered floor.

Grunting, he struggled with Holtzman, and all he saw was the mask of his thirty year old demon. "BECKETT!" he cried out.

"How did you find me?" It was the last thing Beckett heard on the phone before she tossed it down on the driver's seat next to her and ran for the barn. Her feet couldn't take her fast enough. Reaching the door, she pulled on it, but it budged only so much before resistance was met. "It's locked!" she called.

The seconds that followed felt like an eternity. She heard commotion inside, and tried the door again, desperation driving every move she made. "BECKETT!" Oh god. The killer was in there with Castle, and he was defenseless. "CASTLE! I can't get in!"

She couldn't hear anything anymore, and for a second, she feared the worst. She strained to listen, and could hear a voice on the other side of the door after a few seconds. "The danger of facing your demons…"

Renewed, she tried the door again, putting all her weight into it as she tried to break it down. It was no use. For a run down barn, the doors were solid and strong against someone like her. "...is sometimes, the demons win."

No. "Castle, what's going on in there! Castle!"

She wanted to kick and scream, and she wished more than anything she had the strength to break down the door and force her way in. She should never have let him go inside unarmed. It was supposed to be a quick in and out job. Go in, take a look around, come back.

Suddenly, a hand shot out under the wood of the door at her feet. She looked down at it, heard Castle's desperate plea. All she could see was the flash of silver. In a knee-jerk reaction, she placed the gun in his hand, and watched as it disappeared back into the barn.

One.

Two.

Three. Four.

Five.

Six.

The shots went off in rapid succession, and Beckett placed her hand on the door, as if that would connect her to her husband somehow. He came out on top… she knew he had. Shaky breaths were all she had left. There was no other possible ending to this scenario. She had seen his hand. He had the gun. He fired it.

He saved himself.

"Castle?" she called, more gentle this time. Seconds ticked. A minute passed. Her hand slipped from the door and she took a step back. "Castle, open the door. Talk to me."

Finally… finally she heard the sound of the beam being hoisted off the door. Wood scraping on wood until it was dropped haphazardly to the floor. The hinges squeaked as it swung only a couple of inches free. She backed away from it cautiously.

When it didn't move any further, and she reached forward with a gloved hand, gently pulling on it until it swung open all the way. "Castle?" she called, taking a small step inside. The body was right there, cloak black as night. If there hadn't been sunlight seeping into the room, it would blend in seamlessly into the background. It was the perfect tool for someone who wanted to be invisible in the darkness; for the man who murdered and was never caught.

The mask was every bit as haunting as Castle had described it. She half expected the blood pooling under the body to be black like the tears on it, not red. Not human.

She gave the body a nudge with her foot while looking around. "Castle?" she called again. Just like that, what relief that was inside her came wooshing out. Castle was nowhere to be seen. He wouldn't just… leave.

Something was going on here...

And then it hit her. She looked down at the body once more, the closed eyes just under the mask. She took in the general bulk of the figure...

"No. Castle! Oh God." She dropped to her knees in the pool of blood and reached for the mask in a panic, praying that she was wrong because it couldn't be real.

There was no containing the wail that escaped her when she saw her husband's face upon pulling the ceramic piece off him. "Rick…" she breathed as tears stung her eyes. Nothing would stop them from falling.

Oh, it hit her hard, then.

She had seen the ring.

She had given him the gun.

She gave Holtzman her fucking gun.

"I'm so sorry," she snivelled, taking a second to brush back Castle's hair.

Then she heard the all too familiar click, and she looked up at the barrel of her own gun pointing at her. Holtzman's face was just behind it, but she was drawn to the silver of his wedding ring more than anything else.

"End of story," Holtzman said, fittingly.

Bang. Bang.