Perez shrugged. ‘She must have been a part of it – of Markham’s murder, at least. The two of them left Fetlar together. The ferry boys said they hadn’t seen the Watts leave the island that day, but Francis took his own boat out. He kept an old van in Vidlin for picking up tools and wood, to use on the mainland. Francis drove Jessie to the Bonhoga, where she had a last attempt to persuade Markham to go south and leave them all alone. Afterwards they followed Markham to Sullom Voe. That must have been a time of decision for them. They could have driven away and caught the ferry home, but Francis wasn’t a man to let him go. By then he was furious and desperate to stop Markham telling Evie about Henderson’s affair and to stop him writing about Power of Water.’

‘Jessie says she tried to persuade him.’ Willow said. She stretched. ‘Stupid, weak woman. She can’t have tried very hard.’

Perez thought that Jessie had spent her life believing that Francis was right. It would be hard to stand up to him about this.

‘So they came back to the Lunna junction to wait for Markham, knowing he’d have to come that way to go home. They won’t have known that he’d arranged to meet Henderson near Scatsta.’

Perez imagined the couple waiting in the tatty white van. There were always vehicles parked at that junction – it was a meeting place for car-shares into town. Nobody would take any notice of them. Perhaps Jessie had prepared a picnic. Something traditional of course: bannocks with reestit mutton, home-bakes. Had the plan just been to scare Markham? To send him on his way? You’ve already broken our girl’s heart once. Now you want to do it all over again. She has a chance for happiness, for a new life with a good man. Or were the elaborate travel arrangements evidence that Francis Watt was already contemplating murder? Perez thought the couple would have spent the waiting time talking about Markham, winding each other up, persuading each other of his wickedness. The tension must have been unbearable as the light faded and the visibility grew poorer.

‘How did they know it was Markham’s car?’ Sandy broke into Perez’s thoughts. ‘The fog would have been so thick by then that they wouldn’t have seen it coming.’

‘But they’d have heard it, wouldn’t they?’ Willow was lying on her side, propped up on one elbow. Her hair had changed colour in the firelight. ‘That engine. There’d be nothing else like that in Shetland. Worth taking a chance on, anyway. Worth starting the van and driving out, causing the oncoming car to swerve into the lay-by. If they’d got the wrong car, they could pretend it was an accident.’