The Doctor had Squidget tucked under one arm (Chantelle could swear it was sniffing the air like a hound with a scent) and was waving her sonic screwdriver with the other, like a buzzing torch. ‘I’m following the trail of agitated air molecules those hovering ’bots leave behind. The trail is thick – really thick – along here …’

‘So, you reckon loads of robots have come and gone this way?’ Chantelle reasoned.

‘I do! And look.’ The Doctor grinned as they came up short against cold pumice. ‘Door in the wall! Combined with the strength of the trail, I reckon this is our way out.’ She did something to the sonic and its whirr changed in pitch.

Suddenly the door slid open to reveal the sand and hard sunlight beyond, stinging Chantelle’s eyes. The Doctor marched straight out, peering around. The Ratt’s kiosk beside the entrance had been left open; well, thought Chantelle, it wasn’t as if anyone was about to nick stuff here.

The Doctor picked up one of the plastic sheets and waved it under Squidget’s virtual nose. Squidget sneezed out a slender nozzle, which stuck to the material, while the Doctor held it up to Chantelle. ‘Look into this, can you?’

Chantelle did so, and with a beep the plastic turned green. Squidget made a low gurgling noise, and the colour of the sheet grew brighter.

‘What’s that thing doing?’ she asked.

‘Accepting these terms that granted you permission to enter before,’ the Doctor explained. ‘My clever Squidget is pushing those permissions through the entire system so now we should be Access All Areas.’

‘Weren’t you already?’ Chantelle said. ‘You’ve got your magic wand for opening doors.’

‘If I’m right about what’s going on here,’ said the Doctor, ‘there are gonna be some doors that no one can open without the most privileged access. But I’m guessing whoever’s in charge won’t be expecting …’ She looked past Chantelle, frowning. ‘Them.’

‘What?’ Chantelle turned and gasped to see a beautiful golden shape slowly, silently gliding into sight. It was roughly spherical, with spires and latticework contained within two spinning, interlocking circles. It looked like some gleaming gold ornament hanging from invisible strings, but she knew what it had to be. ‘Is that a spaceship?’

‘An Astingir War Chariot,’ said the Doctor grimly. ‘Legate Aquillon followed me here.’

I’m dreaming, Chantelle thought, scared but held spellbound by the eerie sight.

Squidget gave a squeak of alarm, jolting Chantelle back to the drama on the ground: two Ratts scuttling out from the shadows towards them, fleshy hoods pulled down over their faces. One held one of the glass-and-metal batons. The tip glowed bloody red and the Doctor shouted with pain, staggered and fell to the ground

The other Ratt started towards Chantelle but stopped at the sight of the War Chariot as it landed gently on the sand. ‘What the frug is that …?’