‘I’m not just a pretty face,’ said Styles, his eyes fixed on the image on screen. ‘And I’m guessing she’s not just here for a breath of fresh air, so worth taking a few snaps to establish her whereabouts, and whoever she might be here to meet.’

‘You think the hubby might put in an appearance?’

‘Your guess is as good as mine, but I’m going to go with no. I think you called it right first time. Whatever she knows, she doesn’t want him knowing.’

Mary Locke headed straight for the treeline at the end of the road. As soon as she was out of sight, Porter started the car up again and drove slowly past the Range Rover. The only other people in view were an elderly couple coming out of the Water’s Edge pub, and a woman coming towards them with a pushchair. She had come from the direction Mary Locke had headed. A dull green gate marked the end of the road and the start of Ruislip Woods. Despite the branches that reached down to obscure the path, several of the gaps in the foliage shifted from green to red and back again as Mary Locke’s coat refused to be camouflaged.

Porter swung into the car park on the left and they walked back down to the entrance. The trees that crowded the gate opened up into a clearing. The path hugged the treeline on the right, and they could see her, red coat seeming to glow every time she stepped from shadow to sunlight.

‘You think we should be laying a trail of breadcrumbs?’ said Styles.

Porter smiled but said nothing. They kept pace with her, careful to maintain their distance while keeping hers in their line of sight. Each time she vanished, they quickened their pace. The path forked ahead and she bore left, away from the lake. The trees grew thicker on their left, a solid wall of greens and browns, oak and silver birch. Porter checked his watch. They had been walking for almost ten minutes at an unhurried pace. He guessed they had covered half a mile, maybe a touch more.

Suddenly she veered left and vanished from view. They broke into a fast walk that made Porter think of the Olympics, how he’d chuckled at the swinging hips of the long distance walkers, how Holly had mimicked their swaying steps around the living room. He pictured the serious look of concentration as she turned a hard right angle in each corner; remembered tripping her up so she collapsed across him on the sofa. He struggled to embrace these glimpses of happier times. They left him with an empty feeling somewhere inside, reminding him that whatever it was, his heart, his soul, it hadn’t fully healed.