He zoomed in further. The image was pixelated on one side, but the other was the rough shape of a bare human foot. Harper’s pulse began to race.

Gideon went on, “The cameras jump at the slightest vibration, causing the images to skip a few seconds, or add trails to the images they capture. That’s what’s happened here.”

“But there are no figures here, just shadows. And a disembodied foot. Jeepers.”

“It’s ghastly,” said Amy, rubbing her bare arms as if she were cold.

Gideon watched the section again, frowned. “I can’t be sure of course, but the shadows there look like glitch trails. As if someone, or more than one person, walked through the screen, and at that exact moment the tape jumped, then cut back in and just caught the trails. I love it. It’s so creepy. Can I have a copy?”

“No,” said Harper. “How can you check if that’s what happened?”

“It’s tricky. The lost section is impossible to recover, because the tape hasn’t recorded it. But if there was something else in the picture that was moving, you would see a jump there too, proving that a second or two is missing. This is so great. It’s brilliant when this kind of thing happens. I’ve used CCTV glitches as visuals at parties.”

“What if there’s nothing else moving in the image? How can we check?”

“How about we zoom in on the nurse’s fingers?”

And there it was. On the screen Anthea Mallison lifted a hand from the keyboard to take a sip of tea. Then the tape jumped, her hand was back on the keyboard and the shadows drifted by. A second or two was missing. Now she’d seen it, it was obvious. But it wasn’t evidence, not if the lost moment was unrecoverable.

“What are you looking for, anyway?” said Gideon.

“An intruder. Someone that a patient said was there, but no one else saw.”

“Awesome.”

“Not for her.”

“The Matrix did this, you know that, right? There’s something they don’t want you to know.” Gideon pulled out his tobacco tin and started rolling a few pinches into a liquorice paper. “Can I get a copy if it’s just for the collection? I wouldn’t share it around.”

Harper gave him a look that he understood meant he ought to give up asking for a copy. What was he gibbering about, The Matrix? Wasn’t that a film? These people were full of conspiracy theories. It was the drugs that did it.

“What did the nurse say?” said Gideon, tapping her image on the screen. “She was there.”

“She said she didn’t see anything.”

“Huh.” Gideon placed the cigarette between his lips and flicked open his lighter. He touched the flame to the tip of the chocolate-brown cylinder and inhaled.