“Sam! We’ve solved the biggest problem in science for two centuries. If the proof stays here, it’ll die with us. This,” and she hit the papers with the back of her hand, “this is the most important thing in the whole world.”

“Stanford’ll work it out. Or Bern.”

“Fuck Stanford,” she yelled. “It’s our work. And there’s no guarantee of anyone ever finding this solution ever again. Three words: Fermat’s Last Theorem.”

“He lied. He didn’t have a proof. Group theory wasn’t even around in the seventeenth century.”

“How do you know? The idiot didn’t write anything down, and it took us three hundred years to do it differently.” She strode over to Petrovitch’s desk and slapped the envelope down in front of him. “Get it out of the city. Any way you can.”

“Pif,” he said, “if I had the rat, which I did for all of half an hour earlier on today, I’d try and mail it to UNESCO straight away.” He picked up the envelope and felt the weight of it before he slid it in his inside coat pocket. “I have something else I have to do. Something even more important than this.”

She stared at him as if he was mad.

“Okay. Listen, because that short-wave radio of yours is going to work and if I screw up, the outside world needs to know this: the AI known as the New Machine Jihad has its physical location in a vault below the Oshicora Tower. The vault is rad- and emp-hard, and I have to assume it has its own uninterruptible power supply. It has to be destroyed. I don’t know if it can migrate to another host, or whether it already has, but if the sun comes up and it’s still in control, someone’s going to have to nuke it.” He raised his filthy bandaged hand and nudged his glasses back up his nose. “Preferably from orbit. It’s the only way to be sure.”

“Sam,” said Pif, “what about science?”

“I think trying to save the world trumps even science.”

She knelt down next to him. “These equations will save more than the world. They’re going to open up the universe to us. Fusion power. Bias drives. Black hole engines if we can find something strong enough to hold one. Space elevators. O’Neill habitats. Generation ships. Colonies on Mars, around Jupiter, in other systems. Flying cars, Sam. You finally get flying cars. And they’ll all be named after you: the Ekanobi-Petrovitch laws.”

He swallowed. How would he do it? Top-of-the-range electronics shop, one that hadn’t already been stripped clean? Charge up the battery pack? Physically take the information with him, maybe. Find a boat dragged loose from its moorings by the rising river and head for mainland Europe. How long would it take? Half a day?