The Doctor shrugged. ‘As far as I could make out it’s a huge collection and transmission relay station, but the technology is really, really complex. And clearly it’s designed to harness time energy too …’

‘So what’s it collecting?’ asked Ryan.

The Doctor shrugged. ‘Not a clue.’

‘I might have an idea …’ Ace was slowly starting to piece things together. She quickly brought the Doctor up to speed about the missing girls, and the reports of strange figures on the streets of Perivale. ‘Reports of alien abductions and an alien ship appearing in orbit around the Moon – surely that’s more than just coincidence?’

The Doctor nodded. ‘Yeah … something weird is definitely going on here.’

Ace was about to tell her about the strange feeling that she’d experienced on the alien vessel, the impression that she’d been there before, when Yaz’s voice rang out across the room.

‘What’s this?’

Ace looked up to see her lifting a semi-transparent sphere, about the size of a marble, from a box full of identical spheres on the laboratory bench.

Putting down her mug, Ace strode quickly across the workshop. ‘I’d be a bit careful with that if I were you.’ She plucked the sphere from Yaz’s fingers and placed it carefully back in the box. ‘It’ll make quite a bang if you drop it.’

‘Ace,’ said the Doctor accusingly. ‘Please tell me that you’re not still making Nitro-9?’

‘Nitro-90.’ Ace grinned. ‘Packs a bit more of a wallop than the stuff you’re used to, Professor.’

‘Explosives?’ A frown crossed Yaz’s face as she glanced at the other half-completed experiments dotted around the lab. ‘You make explosives here?’

‘I make lots of things here,’ said Ace defensively. ‘The explosives are just a hobby.’

‘That’s some hobby!’ snorted Ryan.

‘I tried making home brew once,’ piped up Graham. ‘That ended up being quite explosive. Bit of a shame, really. I was letting it ferment in the airing cupboard … Ruined all of your gran’s pillowcases.’

Ignoring the look that Yaz was giving her, Ace closed the lid of the box and placed it in a tall, refrigerated cabinet alongside several other boxes. She was kicking herself for having left the box out and open. The problem with spending so much time working alone was that it encouraged bad habits. She would need to be more careful in future.

Before Yaz could ask any more awkward questions, Ace’s phone rang. It was Sanaul.

‘Hi Sanaul.’ Ace answered it straight away, grateful for the interruption. ‘What’s up?’

‘Miss Dorothy, I’ve got that information that you wanted about the young lady from the documentary.’

Snatching up a pen and paper from the laboratory bench Ace scribbled down the name and address. ‘That’s great, San. Good work.’

‘And the vehicles that Miss O’Connor requested on your behalf should be waiting for you. A couple of company Range Rovers.’