It paused.

Thea couldn’t see what had caught its attention. In her imagination she saw dusty footprints and long sweeping curves in the dirt where they’d moved furniture. Sweat pricked out on her temples. Had they kicked over their tracks?

If they hadn’t, a siren would soon sound, flashing red lights would swirl over them, and a team of heavily armed guards would burst through the door—

The light moved on.

One long breath out …

How long did a drone battery last? Thea had absolutely no clue. But it couldn’t last forever. That one must have used up a lot of its power playing its part in the explosion. All they had to do was wait it out. At some point it would have to go back to its … hive, or whatever, and they could make a break for it. Unless they just sent new ones. Thea told herself not to think about new drones with freshly charged batteries.

‘Thea!’ Rory hissed and pointed at Rosie who was shaking. No, not shaking, she was in the middle of a fit: hard, jerking shakes made her body twitch until she slipped down into a heap onto her side. Thea’s heart lurched.

‘Can it hear us?’ she asked.

‘I don’t know,’ Rory said, his voice low, ‘but we’ve got to keep her still!’

The tracking light continued its orderly search of the room, each slow arc taking it just a little nearer to where they crouched.

Thea immediately knelt next to Rosie, not sure what to do, not needing a scissor stab to keep her awake anymore. A weak humming sound came from Rosie’s froth-flecked lips. There was something she should be doing, Thea was sure, but all she remembered was that someone in a fit could swallow their tongue, or bite it off, and she tried to keep Rosie on her side.

‘What’s happening to her?’ Thea’s voice shook and she turned to Rory who frowned.

In the gloom, Rosie’s face became Ethan’s and Thea was instantly back at the lighthouse. She could feel the rough carpet under her hands. That moment when she’d known that she’d been wrong to trust Kyle, the moment she’d reached out to knock the headphones away, and Ethan’s eyes turned from panicked but still his – recognisably Ethan’s – to … nothing. No one’s. Another person she hadn’t known how to save.

‘What do we do?’ She looked to Rory.

The light completed another arc and swung closer.

Thea tried to work out angles. They were under the window, through which the beam of light shone. Surely it wouldn’t be able to scan the small space directly under it; surely it would have to stop? Thea noted with relief that no other window provided it with a better view.

‘We’re going to have to keep as close to the wall as we can,’ Rory whispered.