During the next few minutes, several people were led up the stairs and in to the quarantine from other departments.
By the time the two men had returned carrying the air purifier, there were seven infected people locked in the quarantine zone.
"Put it here," Beckett said, standing up and tapping her desk. Re-adjusting her mask, she began to unwrap the layers of plastic from around the device.
"It's so small," Castle said, a little surprised. Perhaps it was the writer in him, but he had imagined a much more sinister looking machine. The air purifier was no more than two feet tall, white and clean-looking.
"I wonder if Lanie could get some prints off this," Beckett said.
Ware, who had been pacing in front of the big plastic wall, stopped. "No way," he said.
"What?" Beckett asked.
"I'm not letting anyone leave that safe-zone in the morgue and you sure as hell aren't taking that contraption in. I've made enough compromises already; you'll have to do what you can here."
Beckett scowled. "We don't have the necessary equipment here."
"Sure we do," said Castle, seized by a sudden idea. "Esposito, can you get me some Scotch tape?" He stared at Castle with a sceptical look on his face before doing what he was told.
"Beckett," he continued, "you got any, like, face powder make-up stuff?"
"Yeah," she said, slowly, looking at him like he had lost his mind. She picked up her bag and started rummaging through it before she brought out some pink blusher.
"Perfect!" Castle said, beginning to get excited. "And a little brush?"
"There's a little brush in it," she said. "Seriously Castle, I don't think this is going to work."
"No, it really will!" he said. "Alexis and I do it all the time when we play Crime Scene Unit at home."
"It's no wonder you and Alexis get along so well," she said, shaking her head slightly. "You both have the same mental age."
"Actually, Alexis is probably older," Castle admitted.
Once Esposito had handed Castle the roll of Scotch tape, he set to work. Popping open Beckett's blusher, he picked up the little brush that accompanied it and dipped it in to the pink powder. Tapping off the excess, he started brushing it lightly over the smooth plastic of the air purifier.
"Well I'll be damned," Esposito said as three fingerprints slowly became visible.
"See?" Castle said, "told you it would work!"
"Do you want a medal?" Beckett asked.
"Kinda."
He took a strip of tape and placed it over the fingerprints, then stuck the tape on to a sheet of blank paper. He gazed proudly at his creation; three well formed, pink fingerprints were now clearly visible, sandwiched between the Scotch tape and the paper.
"That's good work, Castle," Beckett said, sounding genuinely impressed. "Prepare yourselves, boys, we're about to find out who is responsible for this act of terrorism."
She slipped the paper in to the scanner and shortly after, the prints appeared on her computer screen.
"Will you be able to get a match on the database from that?" Esposito asked. There was something about his voice that made Castle peel his eyes away from the computer screen to look at him.
"Beckett," he said, quietly. Hearing the concern in his voice, she turned to look at Esposito, too. He was sweating profusely. Even as they watched, he swayed where he stood. His breathing was fast and shallow; Castle was surprised he was still standing, let alone contributing to their conversation.
"Ware," Beckett called. The Department of Health official came over, took one look at Esposito and led him through the door to quarantine. To Castle's surprise, there were now at least fifteen infected people lying in the fold-up beds behind the plastic wall.
Beckett tore off her surgical mask and threw it to the ground.
"What are you doing?" Castle asked, alarmed.
"Esposito was wearing his mask and he still got infected, so what's the point?" Watching her second friend be led in to quarantine seemed to have pushed her to the edge of hysteria, but before she could say anything else, the computer made a loud beeping noise.
Castle and Beckett both looked at the computer screen and their mouths fell open. On the monitor were the results of the fingerprint scan, and, filling the screen, was a picture of Greg, the suspect who was lying six feet away from them, on the other side of the plastic wall.
"Esposito!" Beckett called. He was standing beside Ryan's bed, but came over to the wall when he saw Beckett. "It's him!" she said, pointing at Greg.
Esposito looked weak and shaky, but when he realised what Beckett was saying he strode straight to Greg, heaved him to his feet and dragged him to the wall to face Beckett. It seemed like his anger towards Greg had made him forget that he was ill at all.
"What the hell!" Greg exclaimed. He was still weak and sickly looking, but at least he could stand.
"Do you have any idea what you've done?" Beckett said.
"I don't know what you're talking about," the suspect said struggling against Esposito's tight grip.
"Don't play dumb with me," Beckett said, get angrier and angrier. "I swear to God, if you don't tell me everything you know about this disease I will come in there and end you."
"I don't know what you're talking about!" he repeated.
"I'm talking about this!" she said, pointing to the air purifier on her desk. "That is what is distributing a deadly virus through this building, that is what is responsible for the death of three people so far and that has your fingerprints all over it, so don't even think about trying to deny anything."
"This is crazy," he said. "I fixed a bunch of those things last week. The guy I was working for, Baxter, said that he had found them in a dumpster and he wanted me to fix them. He said he was going to sell them on. But I swear I didn't know anything about this freaking virus thing, man."
Castle pulled off his mask and turned to Beckett.
"So Harvey Baxter is responsible for rigging the air purifiers with the virus."
"Which means he is the terrorist," Beckett said, turning her back on Greg.
"Baxter said he knew the biologist, Davidson, maybe they were working together?"
"Yeah! Davidson worked at Columbia University and they have a huge Infectious Diseases department. That would be the perfect place for him to create a virus!" Beckett said, stepping closer to Castle, excitedly.
"But then after Davidson had helped him create it, he was dead weight, so Baxter killed him!"
"But why did Baxter turn Davidson's house upside down?" Beckett asked, frowning. "What was he looking for?"
"Research?" Castle guessed. "Incriminating evidence?"
They both stopped and stared wide eyed at each other. "The cure!" they said at once.
An hour later, they received a call from two detectives from the Midtown South Precinct who had gone to investigate Baxter's repair shop. He was nowhere to be found, nor was any evidence of a cure. They had, however, discovered that he lived in the apartment above the shop. They also searched the apartment but there was nothing to be found.
Beckett slammed down the phone.
"They couldn't find the cure," she said, running her hands through her hair. "Baxter must have bolted and taken it with him."
"Or he never found it in the first place," Castle suggested. "It could still be in Davidson's apartment."
Beckett looked up suddenly.
"Castle, you're a genius!" she said.
"I know," he said, smiling proudly.
Beckett called the Midtown South detectives back and told them their latest theory. But yet again, they came up dry. The cure wasn't there either.
Beckett looked through the plastic wall to Ryan and Esposito. Ryan was lying in bed, barely conscious with a drip in his arm while Esposito sat beside him, his head in his hands. Beckett put her own trembling hands to her mouth as she watched her two best friends.
"They're going to die, Castle," she whispered.
"They won't, they'll be okay. You know how tough they are."
"Face it, Castle," she said, more angrily, "there is no cure. They don't stand a chance and it's only a matter of time before we get infected. We're sitting in a room with the source of the virus, for God's sake!"
Castle couldn't think of anything to say. Everything Beckett was saying was true, but he didn't want to admit it. He hadn't even called his mother or Alexis to tell them what was happening because that would make it real. He just grabbed a bottle of water from Ryan's desk and handed it to her.
"Here, get some water inside you. It'll do you good."
"No, having the cure inside me will do me good," she said, pushing the bottle away.
"Having the..." Castle repeated. "That's it!" he exclaimed. "What do you do when you lock something and you don't want anyone to find the key?"
She paused for a moment, unsure of what he was suggesting. But then a look of comprehension dawned on her face. "You swallow it!" she said.
"Davidson drank the cure!" Castle said. "Lanie told me he had a weird mix of drugs in his system. That must be the cure!"
Beckett grabbed her phone, dialled Lanie and put it on loudspeaker.
"Hey, Lanie," she said urgently.
"Kate! You okay?"
"Fine, look, I think we've found the cure!"
"Are you serious?"
Castle interjected "That's what the mix of drugs in his system is. He swallowed the cure so Baxter couldn't get a hold of it!"
"Who is Baxter?" Lanie asked, confused.
"It doesn't matter," Beckett said, "do you think you could work out the cure from the drugs in Davidson's body?"
"Hell, Kate, I'm in a morgue with thirty other people, I can hardly move, let alone concoct an anti-viral drug."
"You have to try," she said.
"Girl, there isn't even a cure for the regular flu, what makes you think this will work?"
"It has to," Beckett said simply.
"I'll try, I will, but I can't make any promises," she said.
"No pressure," Beckett said, with an attempt at a smile.
"No pressure," Lanie agreed, before hanging up.
Ethan Ware had been listening to their conversation and immediately instructed any spare medics to go to the morgue and help Lanie with the cure.
"See?" Castle said, "the cure is on the way. We'll be fine."
Beckett gave a little sigh of relief but as Castle looked at her, he saw her eyes lose focus. Her face blanched and she collapsed to the ground at his feet.
"Kate," he choked. He fell to his knees beside her. "No, no, not now," he moaned. "I can't lose you now."
A/N Thank you so much for reading and thanks to those of you who are subscribed, I really appreciate it. Please review if you have a minute, your comments make my day!