Call it what it is. Murder.

“I think I’l try self-help first,” he said. “Cold showers, long runs, inspiring literature. That kind of thing.”

Parangosky winked. “Talk to her. If Serin’s okay with that.”

Phil ips had never spoken to Halsey. He had that curious look on his face, that go-on-please-invite-me look, but Osman swept right over it. “Go see her if you need to, BB.”

“You know she wiped part of Cortana’s memory, don’t you? If I come back a complete vegetable, you’l know who to blame.”

Sometimes BB wanted to flounce out, but he couldn’t. He couldn’t leave when he was already everywhere, and he needed to create a gap in his memory to ignore anything his sensors were aware of. That was the whole problem in a nutshel . Gaps. They hurt. Memory was his body; he couldn’t just lose chunks of it without consequences, without those mil ions of connections knowing something was missing like an amputee’s phantom limb.

Sometimes he had to partition data so that he had to actively seek out memories rather than live with them lurking in the background, but that was messy. The only way he’d coped with knowing about Osman’s family history was to firewal the data so that it wasn’t on his mind every time he talked to her.

Osman took the radio out of her pocket. “What do I do with this?”

“Give it to Phil ips, because he’s got hands. Then he can accompany me to a secure terminal.”

There. He’d done it. He couldn’t back out now. Osman gave him a sad little smile and handed the radio to Phil ips, who set off on the long trip to the engineering section. Neither of them said a word until they were in the elevator.

“It’l be al right, BB.” Phil ips pressed the radio’s case. “You know what the awful thing is? That I could switch off this BB and he didn’t mind. I actual y forgot he was stil here. He doesn’t interrupt. He doesn’t join in. I told him he’d remember who and what he was, though. Because he’s stil you.”

“You’re real y quite sentimental, aren’t you?”

Phil ips looked hurt for a moment. “Yeah, I think I am.”

A marine was on sentry duty at the ladder to the engineering section. It was probably to make sure Halsey didn’t get out rather than to stop anyone getting in. She was three compartments along on the main passage, her back to the door and her head bent over a desk.

“Dr. Halsey,” BB said. “Have you got five minutes?”

She turned around and gave Phil ips a long, appraising stare, then glanced at BB’s avatar. She had one of those half-smiles that had nothing to do with humor.

“You said that without moving your lips.”

“Yes, I’m just the help, Doctor,” Phil ips said. “That’s BB. I’m Professor Evan Phil ips. I didn’t get to meet you on board Port Stanley. I’m ONI’s Sangheili analyst. But at the moment, I’m BB’s bagman.”

BB noted that he didn’t mention the university at al . Now that was a sure barometer of his sense of identity. Halsey looked over BB, not softening one bit.

“I didn’t meet you, either, did I?” she said. “BB. ”

“Black-Box, Dr. Halsey.”

“So which ship or Spartan are you assigned to?”

“I work for Captain Osman.”

“Oh. Is she here?”

“Yes.”

Halsey didn’t quite flinch but her pupils dilated a fraction. “Wel , I don’t suppose I deserve a box of chocolates. How about Naomi?”

“She’s in Port Stanley. Playing cards with the ODSTs.” He listened in via the alarm system in the corvette’s wardroom. “She’s not winning, but then maybe she’s not trying.”

“So … what can I do for you?”

“I may have to reintegrate a damaged fragment. It was security-purged as wel , so is there some way to avoid creating time baseline discontinuity? I know you wiped a chunk of Cortana and she didn’t realize it, so how about tel ing me what you didn’t record about the algorithm?”

Halsey crossed her legs and sat cupping her elbow, eyes narrowed. “I’d love to know who built you. That’s quite impressive decryption.”

“I’m designed to be completely fabulous. So is there a way around it?”

“If you hacked my files, then you’d know I didn’t find one. Although I can obviously fool an AI into not knowing data’s been deleted.” She looked up at Phil ips. “Do you know what this is about? The time baseline’s a little like the system clock on a dumb computer. It’s the AI’s sense of reality, for want of a better word. If there’s a gap, it’s like staring at yourself in the mirror and not seeing part of your face. Or that name on the tip of your tongue that you can never recal even though you know your life depends on it. Or a missing limb.”

“I think he gets it, Doctor,” BB said. “Never mind. I knew it was a long shot asking you to fix a fourth-gen.” See, I can be a bitch too, dear. “You’ve been out of the field a long time. I’l work it out for myself.”

“Fourth generation.”

“Yes. An AI built by AIs.”

That made her blink. “I’ve been kept out of quite a few loops, haven’t I?”

“God, yes.” BB twirled around to face the door. “Thanks, anyway.”

Phil ips was very good at taking cues as wel as carrying things. He fol owed BB down the passage into one of the server compartments, stil clutching the radio like it was an anesthetized scorpion that was about to wake up any second.

“Is that true?” he asked. “That you were made by another AI?”

“Not real y. Look, plug the radio in to that dock, wil you? Thanks. No, I just lobbed that in to see if she’d bite. She’s upset that they kept Infinity from her, and the Spartan-Threes, and the Spartan-Fours, and even the monthly menu plans. She’s rather like an AI, you see. She has to know things or she’l burst. If she knew anything that could fix the time baseline, she’d have bargained with me.”

“You think she’s got a personality disorder?”

“No, she’s just a nasty bitch. An unpleasant personality isn’t a medical condition. Just a symptom of not being slapped around the head enough.”

“Wel , thank you, Dr. Freud. We’l be in touch.”

Phil ips forced a smile and pressed the radio down into the dock with a soft click. Now BB could see himself, a glimpse in a mirror that was his precise reflection but not the three-dimensional reality of him. The next process was to step into that image like a coat. It usual y took a fraction of a second. This time, he’d have to take each segment in stages. He’d check it out, integrate it, and see how suffocatingly empty it felt.

“She might stil come across,” Phil ips said. “Give her some time.”

“She doesn’t know the answer, we could be running out of time on the Halos, and we real y need to crack on with Venezia.” BB would deal with it.

If Cortana had coped, then so could he. “She can ram it, as Mal would say. I’l fix myself, thanks.”

“That line she came out with about the gaps. Was that accurate?”

“For an AI, not acquiring data and making sense of it is like suffocating. It hurts and eventual y you die.”

Phil ips held up his hands. “Sorry. I’l shut up. Is there anything I need to do?”

“No. It’l be over before you know it.”

BB’s life was lived at a speed that humans could calculate but never experience. Before Phil ips had even lowered his hands, BB would work through every segment of the damaged fragment, explore its data and processes, try to recover deletions, and align both time baselines. Then he would see the gaps, the bottomless shafts, the paths that led to doors that opened into nowhere. He would try to knit reality back together, assembling al the inputs his fragment had experienced at precisely the time they’d happened, and match them to the processes the fragment had been running. And he would know what he could never repair and had to live with. Once he tested it and found the voids, it was already too late.

Awareness of them made them part of him, and he could try to firewal the worst ones, but he could never remove them or refil them. He could never un know anything.

And now he was communicating with that damaged reflection.

He blurred. His intact self had no precedence over the other. They were simultaneously both him, warts and al .

Is this what I am, an intelligence AI? Is this what was purged? Phillips told me all this. God, how could I function without knowing all this? I didn’t know who I was. I don’t remember Phillips. But I do. Is this version of me actually real? Did I do all those things? I can fly that ship. I can fly this ship. And … I was prepared to kill Phillips.

BB swal owed the unknowns and the knowns and al the shattered, shapeless debris that would never fit into him again just as Phil ips dropped his arms to his sides.

“You okay, BB?” Phil ips asked. “Is it done?”

BB felt that the world had shifted along an infinite fault line. He composed himself as best he could. “Wel , I certainly recorded an awful lot of material in Ontom, didn’t I?”

“You’re okay, though, aren’t you?”

No. I’m not. BB had talked to Vaz about the time he’d been wounded and almost choked to death on his own blood. Vaz had described drifting in and out of consciousness, recal ing things that hadn’t happened but not things that did, and feeling he wasn’t the same person when he final y recovered. That must have been a lot like the way BB felt now. Vaz had bounced back. Humans could accept their fal ible brains.

But I am a brain. That’s the fallibility that’s waiting for me, that’ll finally kill me. That’s where it’ll all end.

That’s a taste of rampancy.

There was a taste of something else, though. Along with the chaos, his fragment reminded him of something Phil ips had said to him in the temple tunnels: Because I’m your friend.

It was oddly comforting. He resolved to do progressive clean reinstal s of his matrix if he suddenly got an urge to acquire a face.

“I’l live,” BB said. A friend. Well, I’ll be damned. “Now let’s see if we can make some sense of those inscriptions.”

UNSC PORT STANLEY, SANGHEILI SPACE: NEXT DAY Vaz was halfway across Foxtrot deck, working out if he could catch the hockey finals on Waypoint and wondering what had happened to the exercise machines, when he suddenly found himself standing on absolutely nothing at al .

It was the blue glow from two deuterium drive vents that did it. One second he was lost in thought and the next he was scrambling for safety. The glow was outside the hull. He shouldn’t have been able to see it. A chunk of Stanley’s hul was gone— But I’m still breathing.

He squatted on the edge of a void, staring down at the vast, light-speckled hul of Infinity as she tilted away from him at a slight angle. His brainstem had done its primal reflex job and warned him he was about to fal down a hole, but his forebrain told him not to be such a dick because it was obviously a transparent hul —a transparent hul that Stanley had never had before.

His heart was stil pounding. “Adj? Adj, can you hear me? What the hel have you done?”

Massively heavy boots clunked behind him. Naomi stepped out onto the transparent surface in ful armor, as if she was making the point that if it could take more than four hundred kilos of kitted-out Spartan, it could cope with a ninety-kilo ODST.

“Clever, isn’t it?” she said. “Transparent metal. Leaks made some adjustment at the molecular level, and—there you go.”

“Why?”

“Why not?”

“A warning would have been nice.”

“Infinity’s got a big transparent dome on her atrium.”

“So we’ve got to have one, too? Who asked for this, or is it Huragok makeover week?”

“Prototype time, Vasya. Procurement and ONI have a stack of new stuff they want tested, so Osman said yes.”

“I bet she didn’t ask for a glass deck.“ “No, that was BB.”

Naomi clonked around on the deck and gazed down at Infinity for a while. Vaz forced himself past his humiliation and edged out onto the glass, but it was oddly disturbing. He real y had to grit his teeth to do it. Naomi noticed.

“You’re a Hel jumper,” she said. “You jump into space from orbit. You had to do high-altitude conventional free-fal just to qualify. Why is this different?”

“It just is. ” It was easier if he kept looking up and ignored his peripheral vision. No, he had to confront this head-on. He forced his eyes down.

Eventual y the sheer scale of Infinity became more riveting than standing on nothing. “I think Hood’s overcompensating for something. Have we even got a dock big enough to take her?”

“No.”

“You think she’s intimidated the Elites enough now?”

“Probably.”

“Okay.” He thought Naomi had come down here to talk, because this deck wasn’t on anyone’s beaten track. But he stil didn’t always read her right. “I’m going to see how Phil ips is getting on with that translation. He’s been up al night with BB.”

Vaz went to walk off, feeling a bit better about himself now that he could move around on the deck without clutching for support. He got to the ladder before Naomi spoke.

“If my dad knew I was okay,” she said, “do you think it would change what he’s doing?”

Ah, that was a relief. She couldn’t put it off any longer. They’d be slipping soon, heading back to Venezia to resume the actual business of the mission after Phil ips’s interruption, and there was no sidestepping the issue of Sentzke being on Spenser’s watch list. She took off her helmet. Vaz was learning to read the language in that, too. It was a literal gesture, peeling away the defensive veneer and opening up to him.