There was an edge in Patrick’s challenge. Sara frowned at him, then grinned. ‘OK.’ She likewise spread her arms and legs. He was right; there was an invisible wall keeping her from falling. She leant further, and then, without warning, the wind relented a fraction and she went, the grass rushing towards her. She felt arms round her chest, pulling her back up and enfolding her, then releasing her.

‘You went too far,’ he said. ‘Lucky I was here.’

‘Yes, too far.’ She felt suddenly embarrassed, foolish even, messing around on an isolated hilltop with a man she might instinctively trust but still hardly knew. ‘Enough of the entertainment,’ she said waspishly. ‘Let’s head down.’

As they reached the plateau’s edge she paused before beginning the descent. The Ribble valley was alight in the late sun, arrows of reddening yellow bouncing off the Black Moss reservoirs below, a few farmhouses and cottages adrift like small boats in a calm sea of green. Remembering the modest streets of Muslim Blackburn, she was mesmerised by the peaceful spectacle below in the dying of the day. ‘You can see why people might want to come to these parts,’ she said, poise recovered. ‘You’d have to travel hours out of London to see anything like this.’

‘You can see why it spooked people too,’ he said.

‘Yes, the Witches of Pendle. I mugged up on them on the train. 1612. Twelve tried and executed. A land of superstition and fraudulence.’

‘Nothing like now, then,’ he said. There was no grin.

That night Sara went over the five files again. First contacts varied between the second half of 2005 and early 2006. There was wider variation in their outcomes.

1)    Asif Hassan, closed in 2006.

2)    Farooq Siddiqi, first contact 2003, ‘exited 2007’, file then closed.

3)    Shayan al-Rehman, ‘contact lost’, file open.

4)    Iqbal Jamal Wahab, ‘returned 2014’, file closed 2015.

5)    Samir Mohammed, ‘closed 2006’.

And there was the link. The one thing common to them all. Should she have bounced it on Sami? No. It would have been a huge risk, a shock tactic that could have deterred him irredeemably. No specific day was given but in June 2006 under ‘Contacts’ there was an entry in all five files. ‘Interviewed by Blackburn CID. Released without charge.’ It gave no hint of the content of the interview. It may not have been proof positive but it gave every sign of a connection.

If only Sami would get back to her, she might have gained enough trust to lure him into giving her the link; but she knew that bird might have flown. She would next try Asif Hassan’s family address; as his file was also closed at the end of 2006, he, like Samir, might just have stayed in Blackburn. Or remained in touch with his family.

Who else was alive? Who, if any, was dead? And how?

What were the files designed to lead her to?