In Gineto’s apartment, Vala spent a chime scrupulously copying Agata’s posture and learning to mimic her gait.

‘No one would mistake our faces,’ Vala admitted, ‘but if I hold this box of books on my shoulder to obscure my face from the camera . . .’ She demonstrated.

Agata had carried Medoro’s real books home in more or less the same way; a second instalment need not attract suspicion. She handed Vala the key to her apartment. ‘Happy reading.’

She waited with Serena and Gineto, practising her imitation of Vala but hoping that no one would even be watching the camera feeds. Let them all be busy following Ramiro and Tarquinia.

Serena checked the clock on her belt. ‘Time to go.’

Gineto said, ‘Good luck.’

Agata followed Serena out of the apartment, trying to appear suitably motherly: mildly affectionate but mostly aloof. Vala had always seemed bemused that two lumps of flesh shed from her body had grown into fully functioning creatures, with no further intervention on her part. The corridor wasn’t too busy, so Serena took the adjoining rope, never concealing Agata entirely from the cameras they passed, but often obscuring part of the view. Anyone with access to the feeds would be able to reconstruct every party’s true movements easily enough, in retrospect – or long before the event, if the information was recognised as important enough to send back – so their not being caught out now would be largely contingent on their not being caught out later. From their position of ignorance, success and failure seemed balanced on a knife edge, but from a cosmic point of view the two slabs of self-consistent events had been utterly distinct for at least the last three years.

As they drew nearer to the utility shaft, Agata could see a camera gazing straight down at the entrance portal. They hung back, and Serena glanced at her clock. ‘Where are they?’ she muttered. A moment later Agata heard a group of people approaching, talking and buzzing.

‘Now,’ Serena whispered. They advanced together. There were a dozen people coming the other way, spread out between the two guide ropes. Some of them, politely, tried to shift ropes to let Serena and Agata pass, but they were packed too close together along both ropes for them to all fit on either one. As the impasse clumsily sorted itself out, two women who looked like mother and daughter managed to break out of the throng and move away. Agata followed Serena down into the shaft and pulled the portal cover closed behind her. If the security sensors here hadn’t been dealt with, they wouldn’t be the first ones to trigger them: the portal’s lock had been snapped a few bells before, and most of the team was meant to have come through before them.