Castle felt a tiny, sharp pain in his arm.
"No," he tried to say. "Can't end like this. Kate, where's Kate?"
He had to tell her - he knew this feeling. Not just the pinprick, but the fog and dizziness and cotton-wool that was invading his brain. It reminded him of something - something Kate should know about -
"Kate."
Through the mental haze, he felt her hand on his face and heard her say again, "Don't leave me, Castle. Stay with me."
Even as the sound of her voice filled Castle with hope, he was still unable to move and his attempts to speak produced no result.
"His pulse is holding steady," said Rita - he recognized that voice now - from somewhere on Castle's left. He could barely feel her hand on his wrist.
"Tell me about Caleb Brown," said Kate's voice.
Yes! thought Castle. If only he could. He'd realized, once Flynn had told him about the incinerator, why leaving Caleb's body in the burnt-out car didn't fit the story. If this operation was run by LokSat, and LokSat wanted Caleb taken out, wouldn't it make more sense to consign his body to the incinerator? So convenient, so final.
Rita was replying to Kate.
"Castle disappeared, and so did you. We thought he might be headed for the precinct, but he never showed, and we had no idea at all that you were going to meet Mason Wood."
"We?"
"Vikram and I. Hayley got hold of me after Castle left the PI office, so I went over to the precinct. I never saw you leave - you're sneakier than I thought."
"I know where all the exits and cameras are," Kate said dismissively. "What then?"
Kate, Kate, Castle was fuming inwardly throughout this conversation. You said you'd stay there, where you were safe, and instead you run off after Wood without a word to anyone. That never, ever ends well.
Then again, he'd done something similar. But then again, at least he'd left word as to his destination. Now he was getting annoyed that his mind was clear enough to have this conversation with himself, but his body wouldn't cooperate enough for him to participate in the other conversation.
"I lurked around until Vikram reported to me that you were gone," said Rita. "I went over to the strip club and found Caleb Brown tossing the place, down to the woodwork, probably looking for clues as to how far your investigation had progressed. He wasn't expecting company."
She sounded justifiably smug.
"What did you do with him?" asked Kate.
"Rendered him inoperative, but alive. I knew about this facility from the old days, so thought I'd bring him along and dust off my in-house interrogation methods. He's out there in the garage, bound, gagged, and strapped down in the SUV I'm driving.
"No sooner did I get inside the garage than all hell broke loose," Rita finished up. "I didn't know about Flynn, or Mason Wood, but I figured if you two were missing and this place was locked down, it might have something to do with our target, so I burned rubber and parked next to the fastest way upstairs. And here you were."
"And this stuff you gave me, to inject him with?" Kate persisted.
"Like I said, a broad spectrum antidote. Standard issue; I recognized the code on the vial while I was rifling Caleb's belongings. It won't hurt him, but it might not help him, if Flynn has come up with something brand new in the neurotoxin line."
Neurotoxin, thought Kate, her mind racing. Something clicked.
"I've seen this happen before," she muttered. "Where have I - "
Something Flynn had said came to Castle's wandering mind. While waiting for his concoction to take effect, Flynn had told him what would happen if his methods proved ineffective.
"A bullet causes death more reliably than a substance which must be diffused throughout the body, but it's messy and too easy to trace. I prefer chemical agents - far less traceable and without all the noise and physical destruction."
Chemical agent, thought Castle. Toxin… why does that ring a bell?
Something clicked.
"Parker," he whispered. "Secretary Reed. The toxin."
"Brad Parker," said Kate. "The toxin he used on Bronson - on Mary Reed."
"What toxin?" Rita asked.
"I'll explain later," Kate replied. "After I save my husband's life. Castle!"
Kate laid her palm on Castle's head. He looked every bit as pale and limp as he had on the lawn outside Reed's house, where he'd collapsed as she'd chased down the man whose stolen toxin was killing him.
"Castle, can you hear me?" She tipped his chin up and carefully lifted his eyelid. "I need to know - is this how you felt when you were poisoned? In D.C.?"
His mouth fell open and his throat worked for a moment. At last he said, "Parker. Bronson. Stolen… chemical."
"If Flynn had that substance in his lab, the antidote had to be there too," Kate said to Rita. "The poison is very fast acting. It's a miracle it hasn't killed him yet. Do you know where the lab is?"
Before Rita could answer, they were interrupted by an unexpected sound - the sound of Kate's cell ringing. She snatched it off her belt and spoke into it.
"Beckett."
"Esposito here," said a brisk, familiar voice. "Your location, Captain?"
"Government building, corner of - "
"We tracked you," Esposito broke in. "Your signal disappeared when you entered the building, but Ryan and I were headed that way anyway. Thought we'd better check on you."
His tone was deliberately casual, but Kate knew him; he was angry that she'd slipped out of the precinct after promising not to - and ended up in this snake pit of an operation.
"I'm in the basement. Castle's here. He's - I think they put something in him, Javi. Is the building secure?"
"We're going floor by floor. Should be clear up to three, which is where we are. And we found our pyromaniac, by the way - once we fought our way in here and stopped whatever he was doing to Castle."
"Tell me what he was doing?"
"He had an IV in his arm - the suspect was about to activate it when Ryan shot the whole bag off the stand. Castle took off to find you and that's the last we saw of him. He was moving pretty fast…"
"Do you have that suspect in custody? Is he conscious?"
"He's right here," said Esposito. "Giving me a dirty look. Forget it, man - I've been glared at by meaner folk than you."
"Hold the phone up to his ear, Jav."
There was a shuffling sound, and Kate heard someone breathing heavily into the phone.
"Is this Flynn?"
A man's voice, strained and angry, said, "Yes."
"What did you give to Richard Castle?"
More breathing and the sound of teeth grinding. Then Kate heard Ryan say, "Castle left him hooked up to this stuff, I don't know what it is. Any idea?"
"Truth agent," Flynn managed to say.
"Oh, so you're under the influence of a truth drug?" Kate asked.
"Yes." Another growl.
"Answer my question, Flynn. Besides the truth agent, what did you give Richard Castle?"
"Nothing."
We don't have time for this interrogation, Kate thought furiously. She closed her eyes and cast her memory back - more than two years back! - and pictured the doctor at Walter Reed telling her about the substance that had nearly ended Castle.
"Tell me this," she said to Flynn. "Is there any amount of the antidote to this toxin in this building?" She named the toxin, as clearly as she could remember it, and held onto Castle's hand -
"Yes," said Flynn grudgingly.
"Tell Detectives Esposito and Ryan where to find it," she ordered. "Espo?"
Esposito came back on the line. "Here."
She told him what to do with the antidote once Flynn handed it over, then ended the call.
"What the hell is that stuff you just rattled off?" asked Rita.
"A classified biochemical substance that Castle was accidentally exposed to, back when I was with the AG's office," said Kate. "If I'm right about these symptoms, and if Flynn was telling the truth about the antidote - it means that someone has gotten hold of the toxin, and that Castle has been exposed to it, again."
"Brava," said a faint voice from the corner. Mason Wood. "Too late, though."
"We'll see," Kate snapped over her shoulder. "He's not dead. He's fighting it."
"He'll lose," Wood went on ruthlessly. "You of all people should know how fast that stuff works. Flynn was preparing to administer it when I saw him last, right before I came to meet you."
"Well, either Flynn waited too long, or there's something you don't know about the toxin," Kate replied. There were more puzzle pieces falling into place in her mind; if Wood and his minion had knowledge and possession of this substance, they had to have connections to the lab where it had been kept. A lab so secret that the AG's office wasn't even aware of its location or its contents until her team came across it while investigating something else.
The sound of someone barreling down the stairs made Kate and Rita reach for their sidearms, but it was a welcome arrival - Esposito with a couple of vials in one hand and his own weapon in the other. He pulled up short, took in the sight of the two women kneeling beside a prone Castle and the prisoner stirring in the corner, and dropped to a squat next to Kate.
"Here you go," he said. "This is the counteragent to the stuff Castle was about to get dosed with when we busted in. So says Mr. Flynn - if you're willing to take a chance on that truth drug he's supposedly under."
Kate was already tearing open the clean syringe Espo had brought with him and filling it with the contents of one of the vials.
"D'you think Castle really was exposed to that toxin, here in Flynn's lab?" Rita murmured. "Could it have been administered somewhere else? Or was it something different?"
"We'll find out soon enough," said Kate.