“Not really.” She pressed her fingers into her forehead. “The only language you speak fluently is mathematics. So what’s the probability of you pulling this off? What’s the probability of you throwing your life away for nothing?”

“That’s why I’m about to swing the odds in my favor.” He closed his eyes, trying to see the number he’d displayed on Chain’s computer while he was supposed to be busy watching Sonja’s messages. “Yeah, that’s it.”

He dialed, and heard ringing.

Then someone picked up and said: “Da?”

“Comrade Marchenkho? It’s Petrovitch. Don’t put the phone down, because we need to talk.”

He lifted the earpiece slightly away from his head as Marchenkho vented his diseased spleen at him down the line.

“Oshicora’s dead,” said Petrovitch when he could get a word in.

“How do you know?”

“His daughter told me. You know of Hijo?”

“Da.”

“Killed his boss. Took control. Occupational hazard for you lot, I suppose. How’s Yuri? Not got an itchy trigger finger yet?”

Marchenkho rumbled. “He says to remind you that his name is Grigori. What is it that you want, Petrovitch?”

“Apart from giving you the glad tidings that your greatest rival has been eliminated? How many men do you have, Marchenkho?”

“Enough,” he said. “Women too.”

“Good, because I want to borrow them. And you too, if you want to come for the ride. We’re going to finish off the Oshicora Corporation once and for all.”

“And when do you propose this happens?”

“That depends. Tomorrow morning good for you?”

Afterward, he started sorting his desk, putting everything into neat piles by subject and looking through his old notebooks, seeing if there was anything else he needed to write.

“Convince me you’re coming back,” said Pif.

“Can’t. Dead man walking now.”

She sighed, and leafed through her own papers, and held up his earlier work. “This is going to be called the Petrovitch Solution, after the man who first discovered it. But I don’t want this to be the only thing the world remembers him for.”

“Most people don’t even manage this: having an equation named after you is immortality.”

“Sam…”

He sat back and stroked his nose. “How long have we known each other, Pif?”

“Two years. Roughly.”

“Those are two years that I stole from someone. I cheated them by living. And for the few years before that. Hang on.” Petrovitch found his bug-detecting wand and made a search of the room. He realized he should have done this before: Chain had had plenty of opportunity to plant one of his bugs earlier.

The lights on the wand flickered into the red as he moved it over his desk.

“Did Chain sit here?”

“Yes. Yes, I think so, while we were waiting for you.”