James looked at him closely and then gave a small, almost-imperceptible nod. “Okay.” And then he did the same to Sally. “Okay.” He reached into his back pocket and brought out a folded and crumpled yellow piece of paper. “A couple of days ago, someone knocked at my door. I don’t really answer it anymore. I know it’s not going to be anything important, and I don’t want to talk to some arsehole about how I need new double glazing. You could say losing a son puts everything into perspective. Still, I wish I answered the door then.

“I forgot anyone had ever knocked, just went on watching television until I fell asleep on the sofa. I woke up in the early hours and went up to bed. Wasn’t until the next morning when I came down the stairs that I found this—” he held up the folded note “—on the damn doormat.”

He held it out to Sally and she took it and unfolded it.

“It took me a moment to realize what it meant. And then it all came flooding back.”

“Who do you think left this?” Sally said, staring at it. From the way she was holding it, Robin couldn’t see what was on the paper.

James shook his head. “I have no idea. Wish I did.”

Sally held the piece of paper out to Robin and he took it. It was a sheet of weathered yellow lined paper, seemingly ripped out of a pad. On it, in hard pencil, someone had drawn four thick parallel lines down the page. They were each spaced out equally, with no deviation. At the top of the page, where the lines ended, there was written an M. At the bottom a D. Two-thirds of the way down the page, just next to the fourth line, there was an X that looked like it had been gone over in pencil about five times.

“What is this?” Robin ran his finger over it and felt the bump that happened when you ran something over too much with a pencil.

“Isn’t it obvious?” James said. “Four lines, four tunnels. M—Marsden. D—Diggle.”

“X marks the spot,” muttered Sally, nodding.

Robin looked at them both, finally getting it. He looked at it again.

“It’s a map.”

Chapter Thirty

Robin was out the door and into the late afternoon air. He heard Sally behind him but he didn’t stop. He was halfway down the street before she caught up, grabbing his arm.

“Robin, wait. Let’s just think about this a bit first.”

He realized he was still clutching the piece of paper, squeezing it so hard it had ripped a little. Sally was looking at him, wide-eyed. He almost shrugged her off and kept going, but she looked genuinely concerned. “What?”