Sayyid’s tone and his assertion of some poison at the heart of the state chilled Morahan. Even more chillingly, he was now being asked to embroil a young woman into a project with unknown consequences and dangers without, he felt, being able to give her the reason why. It was one thing to tell her that he had been approached by an apparent whistleblower calling himself ‘Sayyid’; quite another to say that Sayyid had specifically pinpointed her as the route to whatever wrongdoing he wanted to expose.

Yet, however much he disliked himself for it, however much he had found Sara Shah a sympathetic, intelligent woman, he must resist the urge to come clean and tell her everything. For now anyway.

‘What are you going to do, Sara?’ her father finally asked, as he sipped his coffee and she her peppermint tea in the kitchen.

She’d explained the job offer but not the events described by Morahan that had led to it. She wished now that she had paraphrased his initial letter for her father, rather than allowed him to read it fully. If he ever knew the full circumstances, he would try to stop her.

‘What would you do in my shoes?’

‘How could I ever be in your shoes?’ he spluttered. ‘OK, let me ask this. Might it put you in danger?’

‘No, Dad,’ she smiled. It was her chance to row back. ‘He was being alarmist.’

‘I’m glad to hear that. So will it be good for your career? That’s the main thing.’

She rose, walked round the table behind him, and gave the top of his shiny bald head a gentle kiss. ‘I love you, Dad. Time to think.’

Two evenings later, mulling for the umpteenth time over the conversation on the Common, Sara sat at her desk staring out over the rooftops, sensing a door closing behind her. The question she’d raised at the very beginning lurked. Why her? Or rather, why only her? Yes, she did not underrate herself; yes, she could see how well-suited to it she must appear. But she was not the only one; to think that would not only be arrogant but untrue. Why was he so insistent?

Over those forty-eight hours memories dogged her with an uncontrollable viciousness. Was it to remind her that she’d once before had her chance to intervene, to save innocent lives? That time she’d failed. Was this her second chance? If she opted out or delayed for a second time now, would those memories ever fade away? Would she be consumed by guilt for the rest of her life?

She began to write the letter. Once it dropped through Morahan’s front door, there would be no turning back. As the thought sank in, she felt a first tinge of fear.

She gathered herself and went downstairs.

‘Dad, would you mind driving round with a second letter? Same address.’

He silenced the TV. ‘What did you decide?’