She led them across the hangar to a service lift that ran up the side of the support gantry. The three of them squeezed inside and they were whisked 80 feet into the air to where the probe sat on top of the first-stage booster.

A tool station sat on the metal gantry next to the probe, and Sam had already removed several plates from the outer hull of the probe, revealing the tangle of fuel pipes and coolant systems of the second-stage engine.

‘I’ve assumed that we intend to launch conventionally and only engage your device once Virgil is in orbit,’ said Sam. ‘I’m guessing there’s no point in advertising to the rest of the world that this is anything other than a standard Moon-shot.’

‘Even so,’ said Will, ‘the rest of the world is going to realise pretty quickly that something’s up if this thing goes as fast as you say it does.’

Dorothy said nothing. The truth was that it wasn’t just the rest of the world that she’d wanted to keep this hidden from; it had been UNIT, Torchwood, the Countermeasures Group and a dozen other government agencies that would be breathing down her neck if they knew what she had …

‘OK,’ she murmured. ‘Let’s do this.’ She placed the box down on the gantry next to the open panel and unsnapped the clasps.

‘Oh, my God.’ Will took an involuntary step back as the lid opened and he caught sight of what was inside.

‘I don’t believe it.’ Sam’s eyes widened and she leaned forward to get a closer look as Dorothy gingerly lifted out the alien drive system and its symbiotic engineer. ‘How on earth do you intend connecting that … thing with Virgil?’

‘Earth has nothing to do with it,’ said Dorothy, reaching inside the open hatch and placing the alien machine amongst the gleaming metal thrusters.

She stepped back, snatching a cloth from the tool station and wiping the grease from her fingers.

‘Interface,’ she barked.

The Squidget exploded into life, thin hair-like feelers erupting from every pore on its body, its skin virtually glowing with energy. Chirruping excitedly to itself, it began to extrude itself into every nook and cranny of Virgil’s engine compartment, the tendrils thickening and hardening as they went, engulfing the metal and plastic of the probe with slick alien flesh.

‘Dorothy …’ The alarm in Will’s voice was clear.

‘Sometimes you just have to trust people.’ She looked at him and found she had to force the smile. ‘Remember?’

‘It’s unbelievable.’ Sam was staring in amazement at the schematic readout on the laptop sitting on top of the workstation. ‘It’s taken that thing less than a minute to bypass the entire ignition subroutine and hardwire itself into the propulsion control systems.’ She looked at Dorothy in astonishment. ‘How is it doing it? Its size seems to increasing exponentially. Where is it getting the additional mass?’