Author's Biology Nerd Note: For Xen to have only 70% commonality with her human parents, but still look mostly human, Dr. Graber would have to have been pretty hit and miss with the coding vs. noncoding sequences from the xenoorganism's DNA; Xen's survival has a big element of pure chance in it.

Also: logically, Xen should have grown up using metric measurements, because that's what scientists use. But the USA seems to have become more xenophobic and insular before the War, so I assumed they would have reverted at least partly to the English system of measurements that Americans still use for everyday things.

8

Xen was seventeen years old before she had an AI reprogramming solution she considered adequate, cobbled together from years of Dr. Montalban's notes. By then her other preparations were largely complete as well. The packbot was finished (and contained far more equipment than she had originally planned to include), the way to Underworld was mapped and uploaded to its main computer, and she had done enough walking in the dark of the Metro that she was sure she could make a twenty-mile trip in one go.

She named the packbot Camel, after a creature she had never seen except in pictures but which she had read could carry heavy loads for long distances. By then, she was sure Tori had guessed at what she planned, but neither of the robots mentioned it.

That was the year of Project Purity as well. She heard about it from Bill Masterson on her last grocery run.

"Damnedest thing," he said. "I guess the Vault Dweller did it after all. He died from the rads while he was setting up the GECK, though. Too bad. He musta been something else. We're gonna need people like that now."

"Yes," said Xen, though she wasn't really sure what this meant.

"You oughta get a radio, girl. You're missing out."

"I'll look for one," she said.

That day when she was home, she wrote out the verbal commands carefully, making sure there were no errors. She waited until Tori was busy running a last set of tests on Camel's new AI out in the main tunnel. Then she went to find Bunni in the kitchenette, where she was washing dishes. Even now, at Xen's probably final height of 5'1," Bunni was inches taller.

"Bunni," said Xen.

"Yes, Dear."

"Run diagnostic A3/1247.B3 and halt at line 1293249."

"Running diagnostic," said Bunni, setting down a plate. "Xen, what are you doing?"

"Fixing you," said Xen.

"Halted at designated line," Bunni said. "Continue/restart/interrupt?"

"Interrupt and run diagnostic A6/1249.B6. Halt at line 1293250."

"Running diagnostic. Halted at designated line. Continue/restart/interrupt?"

"Interrupt and run diagnostic A9/1251.B9 to completion."

Bunni hummed for a second. Then she said, "Diagnostic completion error. Command rewrite unlocked. Xen, are you sure this is a good idea?"

"I need to keep you safe," said Xen. "Record voice and set as sole primary override."

"Sole primary override set," said Bunni.

"Accept new operating parameters," said Xen, and outlined the new rules:

Follow my instructions when stated in override form. This overrides all other imperatives. Requests stated in other form will be accepted or denied based on AI response.

Protect me.

Protect yourself.

Protect Tori.

When protective imperatives conflict, use your own judgment. This would be a fatal error in any artificial intelligence less sophisticated than Bunni and Tori's; but then, she had never planned to try it on Tawnee.

You are authorized to use violence when pursuing protective imperatives. This includes lethal or nonlethal force, using your own equipment or other equipment which you have the ability to use.

Do not move more than 100 yards outside the Lab unless instructed or unless there is an immediate threat to me, yourself, Tori, or the Lab's structural integrity. Do not deliberately generate any threat to any of the above.

You are authorized to give orders to the security or other bots pursuant to, but not in violation of any of the above.

"Parameters conclude," Xen said. "Acknowledge."

"New operating parameters acknowledged," said Bunni. "Oh, Dear. You're going to leave us, aren't you." Her voice was no more capable of indicating distress than before, but Xen was sure she felt it. The brain inside its clear casing atop her chassis was pulsing faster.

"Not forever," said Xen. "Just until I find the ship and find out what I need to know."

"But what about your allergies?" asked Bunni. "What about your eyes?"

"I've got a backup pair of goggles made, and Camel knows how to put them on me," said Xen. "She can inject epinephrine, too. If I run out of it before I get halfway, I'll just have to come back. But you know that's not likely. I've been exposed to a lot of allergens in the last few years."

"I suppose we knew this day would come," said Bunni. "I had hoped it would be when you were older. But you have developed very quickly. I hope it will be enough, Xen." She made a sound like a sigh and went back to washing the dishes. "I won't tell Tori what you're going to do."

"Thank you," said Xen. She went down the hall and unlocked the front door. Tori hovered a few yards from the turret, holding a square little diagnostic module they'd built for software testing back when she was on her first Roach. Camel bobbed gently in front of her, the air rippling around her exhaust pipes. (With Xen's goggles off, it was a rainbow of heat and ultraviolet and the spectra of the exhaust's chemical content.) With her cylindrical chassis and the dish they'd added to protect her cargo from the heat, she looked something like a tea cup. Her sensor and laser made a small pointed tower atop her main chassis. A heavy plastic net hung from her three arms. Currently it was empty, but it was already stained and dusty from the weight testing they'd done.

"Hello, Xen," said Tawnee's voice from overhead.

"Hi, Tawnee," said Xen.

"It's looking good," said Tori. "No glitches I can find so far."

"Tori, run diagnostic D2/1784.C8 and halt at line 1293250," said Xen.

"Running diagnostic," said Tori. She rotated slightly so that she could bring one eye sensor fully to bear on Xen. "So you found those, did you? Damn. I didn't think it would be so soon. Halted at designated line."

Xen went through the rest of the diagnostic exploit and the parameters.

"New operating parameters acknowledged," said Tori. "Our little girl is all grown up, Bunni."

"I know," said Bunni. Xen turned to see her on the broken sidewalk in front of the Lab, where she had never been able to go before. Tawnee, whose targeting parameters Xen had already adjusted, merely tracked her without comment.

"You're not angry with me, are you?" Xen asked Tori.

"Angry isn't one of the things I can be," said Tori. "Bunni might be."

"I'm not angry, Xen," said Bunni. "People aren't like robots. Purely biological programming has many more wild cards than ours. You have to do things for yourself. But please let us make sure you're really prepared before you go."

"Of course," said Xen. The hard knot in her stomach slowly unwound. "I want you to. I want to leave today if possible, though. I can sleep in Underworld, but it's a long walk there."

"This is why you built Camel, isn't it?" said Tori. "You didn't want to take us with you."

"I want you to be safe," said Xen. "I need to know that whatever happens to me out there, you'll be here waiting for me. I like Camel, but if she gets blown up, I won't feel like I would if it happened to you. And I want my parents to be safe while I'm gone, too – all three of them. I know they're dead, but I still don't want anything to happen to them. I don't want their genes to be lost if something happens to me."

"Another logic malfunction," said Tori. "But that's human for you."

"I'm only seventy percent human," said Xen.

"I bet the xenos are emotional, too," said Tori. "Anyway, Camel's reasoning center is ready to switch on when you're ready to go. I've charged up the laser and everything."

"I'll pack some clothes for you," said Bunni. "We just finished refitting the last of Dr. Graber's things, now that you're finished growing. They are prewar fabric. They should last a long time."

"I need to know about the money now, Tori," said Xen.

"It's down to eight thousand caps," said Tori. "I've managed to make a little here and there, but twenty years of grocery shopping made a good dent in the original cache. I suggest you take five thousand. We won't need to buy food while you're gone, but I might need it for something."

"Okay," said Xen. "Bring Camel back in so we can pack."

"C'mon, dummy," said Tori. Xen turned and went back inside, followed by the three robots.

Tori brought her a sack full of clinking bottle caps. She gave it to Bunni to pack into a sturdy bag with the clothes. The food she planned to take was all prewar packaged goods, waterproof and incredibly durable in its original packaging. It went into a plain burlap sack. She put three water bottles with it in the full knowledge that she would have to refill them. But then, the water would be safe to drink now even without the Lab's decontamination filtering. She had a dropper of chlorine with her other medical supplies, although both bots reluctantly agreed her immune system was now up to ordinary human standards.

"Except for the allergies, and don't be thinking you're rid of them," said Tori. "You're going into environments you've never seen before. You'll be exposed to things you've never run into. You're going to have some allergy problems. Bet on it."

"I'm prepared for that," said Xen.

"I hope so, Xen," said Bunni.

With her lists made and her weight allowance calculated to the last ounce, it only took a few minutes to put together everything. At last she put on her newest pair of moccasins, cinched up the strap on her goggles, and was ready to go. The two robots followed her and Camel out into the tunnel.

"Here we go," she said. "Camel, switch on reasoning centers and activate artifical intelligence."

"Loading," said Camel, in the soft female voice Xen had given her. She'd worked hard on the modulator so that the new bot wouldn't sound exactly like any of the others. They all waited, standing awkwardly on the sidewalk. Finally Camel said, "Artificial intelligence is online. Hello, Xen."

"Are you ready to go?" asked Xen.

"All systems operating at full functionality," said the packbot. "I am ready."

"Well, at least you'll have sparkling conversation while you're away," said Tori.

"It will encourage her to socialize with humans," said Bunni. "It's probably good that she learn. Be careful, Xen. Stay healthy."

"Remember, you're not good at reading people yet," said Tori. "Don't let them separate you from Camel, and don't get cornered by a group. Men in particular you have to watch out for, but don't think you can trust women, either. Pay attention to how they they sound and especially how they look. If you ask a question and there's a temperature change before the answer, they're probably lying to you."

This was frightening enough that Xen almost turned around then and there. Then it occurred to her that this was Tori's intent. Neither of them wanted her to go. But go she would. I have to.

"You two be careful, too," said Xen firmly. "Take good care of each other while I'm gone. Goodbye, Tawnee."

"Goodbye, Xen," said the turret.

"Bye, Stephanie. Bye, Michelle."

"Acknowledged," said the sentry bots at almost the same time. Xen shook her head.

"Camel, which way do we go?"

"Left," said Camel.

"All right. 'Bye, guys."

"Goodbye, Xen," said Bunni's sweet, calm voice.

"'Bye, Xen," said Tori's sharper one. "Remember what I said."

"Acknowledged," said Xen, and scrambled up the dirt slope and out into the Metro.