Banks saw that Nowak was right. Without the CSM’s trained eye, though, the disturbance to the ground would have been easy to overlook.

“Unfortunately, there’s no telling when this occurred,” Nowak went on, “but you can also see that this area has been reasonably well sheltered.”

They looked up. Banks saw that above them stretched a perfect canopy formed by the overhanging branches and light green leaves of the trees.

“It doesn’t mean nothing got through, of course,” Nowak went on, “but it would certainly have kept out a good portion of that shower.”

“Annie said you’d found something,” Banks said.

“Yes.” Nowak walked over to the shrubbery at the base of an ash tree and used a stick to lift up the hanging fronds and branches. “Look here.”

Banks’s knees cracked as he crouched. At first it was too dark to make out anything much at all, but then he saw that some of the lower leaves were dotted, or smeared, with a dark substance.

“I think it’s blood,” Nowak said. “Anyway, we’re taking samples, and Jazz should be able to determine pretty quickly if it’s human and, with a bit of luck, whose. Don’t get your hopes up yet; it could be animal blood. A bird killed by a cat or something.”

Banks stood up slowly. He found that if he got to his feet too suddenly these days he became dizzy. His doctor said it was due to a drop in blood pressure, most likely because of the medication he was taking, but if he had any other symptoms, such as fainting, chest pain, headaches or heart palpitations, he should come back immediately. He didn’t have any. Not yet.

“Good work, Stefan,” Banks said. “Anything else?”

“Quite a lot, actually, but we don’t know how much use most of it is.”

“Anything you think I may be interested in?”

Nowak pointed to a nearby tree. The long grass at its base was flattened in one spot. “Near that tree there, we found these.” He held out a plastic bag containing what looked at first like two cigarette ends, but on further perusal turned out to be roaches.

“So someone’s been using the park as a spot to smoke up,” Banks said. “That’s hardly surprising with the decent weather we’ve been having lately.”

“Again, we don’t know if this is from before or after the murder, but it was under the foliage there, and there’s a good chance there might still be DNA.” He then brought out another package. “With this we’ve got an even better chance, though. Chewing gum.”