Petrovitch walked over slowly, still clutching Pif’s phone. He took Sister Madeleine’s wrist down from its height and turned it so he could see if it was the same number.

“There’s no one there,” she said, “not even breathing.”

He leaned in and she pressed the speaker against him. It was just dead air, not even the hiss of an open microphone or a digital click. Then the line fell dead.

He straightened up and searched the ceiling of the restaurant. There were cameras in each of the four corners, and another over the door. There were half a dozen other people eating; the place was usually busier.

“I think someone’s trying to contact me,” said Petrovitch.

“Why don’t they just call you?”

“I don’t have a phone. I know I must be the last person in the Metrozone not to have one, but there you are. I’ve never needed one. I’ve no one to talk to.” Petrovitch pushed his glasses up his face and glanced across at Chain. “One-three-five, seven-one-one, one-three-one, seven-one-nine?”

He nodded. “You know the number?”

“Yeah. Just never expected to see them like this. I’m going to get my clothes on before I’m forced to run naked from the building chased by ninjas, which is probably where this is going.”

Petrovitch forced a smile at the kitchen staff as he raced around, picking up his boots, socks, trousers, pants, T-shirt. He struggled into his trousers and put his warm, stiff boots on. Then he waved his goodbyes, still wearing the white coat and carrying what he hadn’t put on under his arm.

“Pif? Phone.” He threw it across the table at her. “Keep the gun.”

“Sam?”

“Back to the lab. I’ve just remembered I can be contacted.”

“The mail servers are down, though.” She put the phone in her bag and slung it over her shoulder.

“I still got in touch with you, didn’t I? Good old-fashioned copper wire.”

The pair headed for the doors, and Chain barred their way.

“You have to explain,” he said.

“If you weren’t such a kon pedal’nii, you’d have worked it out.” Petrovitch darted to one side, Pif the other.

She shouted back, “First eight primes,” just before the doors swung shut again.

“You told him!”

“Your tame nun wanted to know, too.”

“She is not my anything.”

“Oh, Sam. I saw the way you looked at her. And she at you.”

He stopped in the middle of the corridor, and she stopped too.

“Never,” he said, “speak about this again.”

“You sure?”

“Yeah.”

“Okay.”

They ran the rest of the way, except for the lift, which was filled with her panting and his soft groans.

When the lift door opened, they could both hear the landline ringing. The security guard caught the barest glimpse of their cards as they dashed by.