Em-Lin stared silently at her sister for a long moment. “The Fuser can do that?” she said.

Or-Lin nodded. It’s one of the functions I worked on. One last booby trap for an occasion like this.

Em-Lin frowned. Apparently, Or-Lin had been even better at hiding things from the link between them than Em-Lin had known.

And the Vorta, their beloved Vorta, had not been solely motivated by altruistic impulses. Even if his dugo tenya were not speaking through Or-Lin right now—and Em-Lin tended to think that it was not—he must have approved the addition of the viral option to the Fuser’s systems.

Either that, or Or-Lin had devised the viral option herself—but Em-Lin had a hard time believing that Or-Lin, alive or dead, would want anything to do with massacring the Federation. Or-Lin had been difficult from time to time, and at the end of her life, she had threatened to seek Division from her sister, but Em-Lin could not believe that she was a mass murderer.

Suddenly, another possibility occurred to Em-Lin. She realized that she should have thought of it before, but she had been so traumatized by recent events that she had readily accepted certain things at face value.

Things like the dugo tenya.

Well? said Or-Lin, still beaming and clasping her twin’s hands. Shall we follow the Vorta once more, my beloved sister?

It could not have been more obvious, now that Em-Lin had finally managed to see through her own veil of shock. Why had Or-Lin gone from, I think I want Division whether you want to go with me or not to calling Em-Lin her beloved sister?

“Let’s do it,” said Em-Lin. It would be better to play along until the time was right. For now, it was enough that Em-Lin had regained a measure of awareness and self-control.

Or-Lin released Em-Lin’s hands and leaped up to give her a quick hug. Oh, sister, I just knew you’d do the right thing!

Em-Lin nodded. In the distance, she heard Gomez’s voice calling to her, and she tuned it out. The only voice that mattered now was Or-Lin’s—but not because Or-Lin was a dugo tenya.

It was because she was something else altogether—yet another application of changeling technology.

All right then, said Or-Lin, swiping a tear from her eye. You need to reconnect with the plasma matrix.

Em-Lin pushed her hands through the morphic skin of the tank and back into the hot, fizzing plasma.

Let’s reconfigure the Fuser to reduce the transmission levels, said Or-Lin. Go to Polyp L3.

“Wait,” said Em-Lin. “First, tell me which polyp controls the viral option. I don’t want to risk activating it by accident.”

Or-Lin leaned close and pointed a finger at a crescent-shaped clump floating upward in the convex tank. “Right there. Polyp Q90. We’ll engage it when we’ve finished resetting the transmitter and eliminated the threat to our people.”

“Thanks,” said Em-Lin, and then she grabbed hold of the Q90 polyp with both hands.

Em-Lin, let go of that for now. I just told you, it controls the viral option.

“I know what you told me,” said Em-Lin. She plunged her thumbs into the claylike meat of the polyp. Immediately, its resident intelligence pinged her mind with fuzzy-feeling thoughts like those of the changeling multitool that she had used to deactivate the quantum bomb.

What do you want me to do? said the polyp.

Em-Lin! Or-Lin’s voice became loud and angry. I said leave that alone and reset the transmitter!

Hello, Em-Lin said to the polyp, remembering her father’s advice.

What do you want me to do? said the polyp.

Stop it, Em-Lin! shouted Or-Lin, her voice boiling with rage. Do what I tell you!

The louder her sister got, the more Em-Lin knew that her theory was right—and the more she knew exactly what she wanted the polyp to do.

Please deactivate the Fuser, she thought.

The Fuser on Zasharu or the Fuser on Mirada? thought Polyp Q90.

Em-Lin had not expected to be given a choice, but she was grateful for it. The sooner the two devices went offline, the greater the number of Miradorn lives she would save.

Both, thought Em-Lin.

No! said Or-Lin, shaking Em-Lin by the shoulders. Stop it or I’ll kill you!

“Shut up,” said Em-Lin. “Just shut up.”

She smiled to herself as she felt Polyp Q90 shut down the system. She had been right about Or-Lin.

Or-Lin was not a true dugo tenya. She was not a remnant of Em-Lin’s dead twin, and she was not a trauma-induced hallucination or dream.

She was the Fuser’s last defense. She was a booby trap.

“The self-determining AI will monitor conditions and take appropriate action.” That was what the Vorta had said.

Em-Lin now knew that that was exactly what the Fuser’s AI had done. Created with adaptive changeling technology, sophisticated enough to manage an accelerated planetary psychic evolutionary process, the Fuser’s AI had been equipped to defend itself against any threat.

Even the threat of Em-Lin herself.

It had conjured the image of her dead sister to distract, confuse, and mislead her. How else to stop someone who had helped build the device from shutting it down? Em-Lin’s guilt at not soon enough recognizing the trap that had killed her sister had given the image more than enough power to twist her.

And in the end, to prevent her from finding the “off” switch, the AI had lied to her, telling her that it was the one thing that it thought she would never touch: the controls of a psychic virus that would murder trillions.

But Em-Lin had seen through the deception.

The Fuser on Zasharu and the Fuser on Mirada have been deactivated, said Polyp Q90.

Thank you, Em-Lin said with her mind. It wasn’t easy to concentrate with Or-Lin shaking her by the shoulders and then beating on her back with her fists, but Em-Lin managed to send another message to the polyp.

Are you capable of permanently deactivating the Or-Lin simulacrum? she said.

Yes, said Polyp Q90.

Stand by, said Em-Lin, and then she yanked her hands out of the plasma matrix. Whirling around, she grabbed Or-Lin’s hands, stopping the pounding on her back.

Or-Lin shivered and sobbed in her grip, her face twisted in an expression of mixed fury and agony. She looked like someone who had lost everything, someone who was completely and irreversibly shattered.

Em-Lin knew that she was not her sister, that she was not anyone at all and never had been. But she looked like Or-Lin, and she sounded like Or-Lin, and she felt like Or-Lin. It was enough for now.

Em-Lin released one of Or-Lin’s hands and reached up to stroke the side of her face. “I’m sorry that I didn’t always do the right thing,” she said. “I’m sorry that I didn’t notice the trap that killed you sooner.”

Or-Lin choked on a sob and shook her head wildly. Don’t do it, she said. Don’t do it don’t do it don’t do it.

“I forgive you for hurting me,” said Em-Lin. “I will miss you and love you forever.”

No, please, whimpered Or-Lin. Don’t do it.

Then, though the woman before her was nothing but an illusion, Em-Lin leaned forward and pulled Or-Lin into her arms. As she hugged her, Em-Lin shut her eyes tight and began to cry, too.

“Good-bye, my sister,” said Em-Lin.

Then, she cast her thoughts to Polyp Q90: Please permanently deactivate the Or-Lin simulacrum.

Done, said Polyp Q90.

“Done,” said Em-Lin, opening her eyes to see Gomez and the other Starfleeters staring back at her. “I’m all done.”