“Crap,” she said, under her breath. Quickly she turned the iPhone around and looked at the screen. It had gone blank. She’d forgotten to extend the time of the auto-lock, and the phone had switched itself off.

“Everything all right, Dr. Grazdani?” called Russ from the desk in front of the lobby.

“Yes, thanks, Russ. I must have blinked at the wrong time. I’ll just try it again.” She smiled over to the men, who waved and went back to their preparations to leave.

The machine reset, and with the image back on the screen of her phone, Pia tried again. After a couple of seconds, in which time Pia thought her heart was going to stop, the usual beep sounded and the green-for-go light came on. A second later the door lock in the glass partition clicked open.

“It worked,” she said, rather too loudly. In some respects she was surprised. It was a good example of technology chasing technology. The designers of the first-generation of iris scanners probably had never imagined the advances in resolution of smartphone touch screens.

“It usually does work,” said Russ, his voice much closer than it had been the last time Pia had heard it.

Pia jumped and turned. The guard was standing no more than six feet away.

“I’m getting a call,” said Pia, who turned back to her phone and went to adjust its display. At the same time she walked through the glass door and into Nano proper. After pushing the elevator button, she turned her head and saw that Russ had retreated back to the main entrance doors and was in conversation with the daytime security shift that had just come on. Pia resolved to be more careful next time.

Next time.

It was early in the morning, so up on the fourth floor Pia passed the door into her lab and retraced her route to the double doors that barred the way onto the bridge. There she tried the trick with her phone again. She had no reason to believe the phone would work when her own eye didn’t, but she wanted to try. When the predictable happened and she couldn’t get in, Pia walked back to her lab. What the hell did Nano have hidden on the other side of that bridge? In her bones, Pia felt it had to be something serious to justify all the security.