Cheng collected his belongings and headed for the exit. Nina, Eddie and Macy started after him, only for Hui to hold Nina by her arm. ‘Please take care of him,’ she whispered.

‘I’ll do everything I can,’ Nina assured her.

‘Thank you. I do not want him to go, but . . . I think he may be as safe with you as he would be here.’ A moment to let the ominous meaning sink in, then she went on: ‘Now, go, quickly. I will catch up.’

Cheng had paused at the door to wait for them. ‘What did Mom say to you?’ he asked.

‘She just wants us to keep you safe,’ said Nina, dissembling a little. ‘Come on. Let’s get out of here.’

Twenty minutes later, the Longitude taxied into take-off position. Despite the frenzied military activity at the base, the seemingly civilian plane was granted immediate clearance to depart. It powered into the sky, turning south.

Nearly another hour passed before a helicopter landed at the bunker. Major Wu Shun climbed out, exhausted. The sun was only just setting, but she felt as if she had been awake for days. She composed herself, straightening both her body and her mind. Grief and pain and rage had to be put aside. There was too much to do.

All trace of the golden pod had been lost once it was out of sight. Like its parent craft, it was invisible to radar, slipping through China’s defences like a ghost. It could be going anywhere – but she had a shrewd idea of who could narrow down the possibilities. Nina Wilde, she had learned, had somehow escaped from the fortress and been brought back to the base. Whatever she knew, Wu was going to find out.

The moment she entered the control centre, she sensed something was wrong. It was not merely because of the city’s destruction; the scientists reacted to her appearance with nervousness, even fear. ‘Where is Dr Hui?’ she demanded.

‘In . . . in her office,’ one of the team replied.

‘And the American? Professor Wilde?’

The man couldn’t hold her gaze. ‘I don’t know.’

Wu gave him a hard glare. He shrank into his seat, but said nothing. Anger rising, she strode to Hui’s office and entered without knocking.

The former director was alone at her desk, drinking tea. The scene’s casual appearance was belied by her hand’s slight tremble as she raised the cup. Wu knew from Hui’s medical records that she had no debilitating illnesses. She was as afraid as the rest of her team.

The major stood before her, hands held imperiously behind her back. ‘Where is Professor Wilde?’

‘Welcome back, Major,’ said Hui, putting down the cup. Its base rattled faintly as her hand shook again. ‘I’m glad you’re okay. My . . . my condolences.’

Wu had no time for fake pleasantries. ‘Something’s going on. Where is she?’

‘I don’t know.’