“It’s one of the crybabies,” the guard told her. “He’s trying to kill one of the psychos.”

Dr. Alycia Liddell swore under her breath and grabbed her keys. Only two weeks into the drug trial and the prisoners were changing too fast, starting to crack.

In the hospital wing, a dozen guards crowded around an open cell door. They were strapping on pads, pulling on helmets, slapping billy clubs in their palms. It was standard procedure to go through this ritual in full view of the prisoners; more often than not they decided to walk out before the extraction team went in.

The shift lieutenant waved her to the front of the group. “One of your babies wants to talk to you,” he said.

She leaned around the door frame. In the far corner of the cell, wedged between the toilet and the wall, two white men sat on the floor, one behind the other, like bobsledders. Lyle Carpenter crouched behind, his thin arms around Franz Lutwidge’s broad chest. Lyle was pale and sweating. In one hand he gripped a screwdriver; the sharpened tip trembled just under Franz’s walrus-fat chin.

Franz’s eyes were open, but he looked bored, almost sleepy. The front of his orange jumpsuit was stained dark.

Both men saw her. Franz smiled and, without moving, somehow suggested a shrug: Look at this fine mess. Lyle, though, almost let the screwdriver fall. “Doc. Thank God you’re here.” He looked ready to burst into tears.

The doctor stepped back from the door. “Franz is bleeding,” she said to the lieutenant.

“Lyle stabbed him in the chest. It looks like it stopped, but if he’s bleeding internally we can’t wait for the negotiation team. I thought you might want to take a crack at getting Lyle to drop the weapon.”

“If I can’t?” But she already knew the answer.

“I’ll give you three minutes,” he said.

They wanted her to put on pads and a helmet, but she refused. Lyle and Franz, like the other 14 men in the GLS-71 trial, were low-risk prisoners: liars, thieves, con men, nonviolent offenders. The review board wouldn’t allow her to enroll the more aggressive prisoners. Still, she’d succeeded in finding men with very high scores on Hare’s Psychopathy Checklist. They were all-star psychopaths–or sociopaths, to use the term some of her colleagues preferred.

The lieutenant let her take only three steps into the cell before he said, “That’s good.”

Lyle’s eyes were fixed on hers. She smiled, then let concern show in her face. “Why don’t you tell me what’s going on, Lyle?”

Franz said, “I’m not sure he knows himself.”

“Shut up!” Lyle said, and the hand holding the screwdriver shook. Franz lifted his chin slightly.

“Just focus on me,” she said to Lyle. “If you put down the weapon, we can talk about what’s upsetting you.”

“I fucked up, Doctor Liddell. I tried to stop him, but I couldn’t–”

“Call me Alycia, Lyle.”

“Alycia?” He looked surprised–and touched. She never permitted the prisoners to call her by her first name.

Franz made a derisive noise, but Lyle seemed not to hear him. “I was doing this for you, Alycia. I was just going to kill myself, but then when he told me what he was going to do, I knew I had to take care of him first.” He flexed his fingers along the screwdriver’s grip. “I stabbed him, going right for the heart. Then he jumped up and I knew I’d missed. I knew I had to hit him again, but I just–froze.” He looked at her, his eyes shining with tears. “I couldn’t do it! I saw what I’d done and I almost threw up. I felt like I’d stabbed myself. What the hell is happening to me?”

That’s what we’re trying to find out, she thought. GLS-71 was an accidental treatment, a failed post-stroke drug that was intended to speed speech recovery. Instead, it found the clusters of mirror neurons in Broca’s area and increased their rate of firing a thousandfold.

Mirror neurons were specialist cells. See someone slapped, and the neurons associated with the face lit up in synchrony. See someone kicked, and the brain reacted as if its own body were under attack. Merely imagining an act, or remembering it, was enough to start a cascade of hormonal and physical responses. Mirror neurons were the first cogs to turn in the complex systems of attachment, longing, remorse. They were the trip wires of empathy.

Except for people like her all-stars. In psychopaths, the mirrors were dark.

“I know you must be confused,” she said. “GLS is making you feel things you’ve never felt before.”

“I even feel sorry for this piece of shit, even though I know what he was going to do to you. What he still wants to do.” He nodded toward the bed. “This morning, he showed me where he was keeping the knife. He told me exactly how he was going to rape you. He told me the things he was going to force you to do.”

Dr. Liddell looked at Franz. The man wasn’t smiling–not quite. “You could have called a guard, Lyle. You could have just warned me.”

“See, that’s the thing–I wanted to hurt him. I thought about what he was going to do to you, and I felt … I felt–”

“Luuv,” Franz said.

The screwdriver’s tip jerked. A thin dark line appeared along Franz’s neck like the stroke of a pen.

“You don’t know what love is!” Lyle shouted. “He hasn’t changed at all, Alycia! Why isn’t it working on him?”

“Because,” Franz said, his tone condescending and professorial despite the cut and the wavering blade at his throat. “I’m in the control group, Lyle. I didn’t receive GLS.”

“We all got the drug,” Lyle said. Then: “Didn’t we?”

Franz rolled his eyes. “Could you please explain to him about placebos, Alycia?”

She decided then that she’d like to stab Franz herself. He was correct; he was in the control group. The trial was supposed to be a double-blind, randomized study, with numbered dosages supplied by the pharmaceutical company. But within days she knew which eight men were receiving the real dose. Guards and prisoners alike could sort them as easily as if they were wearing gang colors: the psychos and the crybabies.

“He’s playing you, Lyle,” she told him. “Pushing your buttons. That’s what people like Franz do.”

“You think I don’t know that? I invented that shit. I used to be fucking bulletproof. No one got to me, no one fucked with me. Now, it’s like everybody can see right through me.”

The lieutenant cleared his throat. Dr. Liddell glanced back. The mass of helmeted men behind him creaked and flexed, a machine ready to be launched.

Franz hadn’t missed the exchange. “You’re running out of time, Lyle,” he said. “Any second now they’re going to come in here and crack you like an egg. Then they’re going to take you off to solitary, where you won’t be seeing your girlfriend anymore.”

“What?” Lyle asked.

“You don’t think they’re going to let you stay in the program after this, do you?”

Lyle looked at her, eyes wide. “Is that true? Does that mean you’ll stop giving me GLS?”

They’re going to stop giving it to all of you, she thought. After Lyle’s breakdown, the whole nationwide trial would be canceled. “Lyle, we’re not going to stop the GLS unless you want to.”

“Stop it? I never want to be the guy I was before. Nobody felt real to me–everybody was like a cartoon, a nothing on the other side of the TV screen. I could do whatever I wanted with them, and it didn’t bother me. I was like him.”

Franz started to say something, and Lyle pressed the screwdriver blade into his neck. The two men winced in unison.

“You don’t know what he’s like,” Lyle said. “He’s not just some banker who ripped off a couple hundred people. He’s a killer.”

“What?”

“He shot two teenagers in Kentucky, buried them in the woods. Nobody ever found them. He brags about it.”

“Stories,” Franz said.

Dr. Liddell stepped closer and knelt down next to Franz’s outstretched legs. “Lyle, I swear to you, we’ll keep you on GLS.” She held out a hand. “Give the weapon to me, Lyle. I know you were trying to protect me, but you don’t have to be a murderer. You don’t have to throw away everything you’ve gained.”

“Oh, please,” Franz said.

Lyle squeezed shut his eyes, as if blinded.

“I give you my word,” she said, and placed her hand over his. “We won’t let the old you come back.” After a long moment she felt his grip relax. She slowly pulled the screwdriver from his fist.

Shouts went up behind her, and then she was shoved aside. The extraction team swarmed over the two men.

Three days later she came down to solitary. She brought four guards as escort.

“You know, you’re good,” Franz said. “I almost believed you myself.” He lay on the bed with his jumpsuit half unzipped, revealing the bandages across his chest. The blade had missed the lung and the heart, tearing only muscle. The wound at his neck was covered by two long strips of gauze. He’d be fine in a few weeks. “ ‘I give you my word.’ Genius.”

“I did what I had to do.”

“I’ve used that one too. But did you have to break his heart? Poor Lyle was in love with you, and you out-and-out lied to him. There was no way you were going to keep him on GLS–you made a petty thief into a suicidal, knife-wielding maniac. How can they put anyone on that stuff now?”

“There’ll be another trial,” she said. “Smaller dosages, perhaps, over a longer period of time.”

“That doesn’t help Lyle, now, does it?”

“He’s going to live, that’s the important thing. I have plenty of GLS left, so I can bring him down slowly. The suicidal thoughts are already fading. In a few days he won’t be bothered by remorse. He’ll be back to his old self.”

“And then someday you’ll get to wring him out again.” He shook his head, smiling. “You know, there’s a certain coldness about you, Doctor–has anyone ever told you that? Maybe you should try some GLS yourself.”

“Tell me about Kentucky,” she said.

“Kentucky?” Franz shrugged, smiled. “That was just some bullshit to get Lyle worked up.”

She frowned. “I was hoping you’d want to talk about it. Get it off your chest.” She turned to one of the guards, and he handed her the nylon bag from her office. “Well, we can talk again in a few days.”

He blinked, and then he understood. “You can’t do that. I’ll call my lawyer.”

“I don’t think you’ll want a lawyer any time soon.” She unzipped the bag and lifted out the plastic-sealed vial. “I have a lot of GLS, and only one patient now.” The guards rushed forward to pin the man to the bed.

She popped the needle through the top of the vial and drew back the plunger. The syringe filled with clear, gleaming liquid.

“One thing I’m sure of,” she said, half to herself. “In a few days, Franz, you’ll thank me for this.”

Daryl Gregory’s short stories have appeared in The Magazine of Fantasy and Science Fiction, Asimov’s Science Fiction, and The Year’s Best SF. His first novel, Pandemonium, was recently published by Del Rey Books.