“Stefan Gilmour is capable of it, isn’t he?” Clarke was gazing at the surface of the canal. It looked dark and oily, and even in daylight would give no hint of what lay beneath.

“No doubt in my mind,” Fox answered. “Way he’s built his empire, he takes no prisoners.”

“I remember reading once that the successful tycoon sees the world the same way a psychopath does.”

“I’m not saying Stefan Gilmour is a psycho.”

“He’s just a man with goals unachieved and successes to protect.”

“You think a forensic psychologist might help us nail him?”

Clarke shook her head. “Let’s stick to what we know.”

“Meaning?”

“We follow leads, Malcolm. Starting with your petrol station…”

The only other customers when they got there were two licensed minicabs. The drivers had parked next to the shop and were inside, drinking coffee from a coin-operated machine and exchanging gossip. Fox made straight for them, pulling out his warrant card.

“Did either of you know Billy Saunders?” he asked.

“Knew of  him,” one driver said.

“Worked for the competition,” his friend added.

“You always use the same petrol station?”

“Tend to,” the first driver conceded.

“Fill the tank, break the monotony?”

“That’s right.”

“Did Saunders use this particular pit stop?”

The second driver shook his head. “Petrol station in Powderhall, far as I know.”

“You never saw him here?”

Fox received a further shake of the head from both men. He thanked them and headed for the counter.

“Nice thinking, though,” Clarke told him in an undertone.

“Saunders drove a minicab, liked the night shift—petrol stations were a second home to him.” He took out his warrant card again and showed it to the assistant.

“You’ve been questioned about William Saunders?” he asked.

The youth behind the counter appeared no older than a school-leaver. His face was peppered with angry-looking acne and his thick black hair looked like it had been styled with a pair of secateurs and a pot of glue. He agreed that he had already spoken with the police.

“And your colleagues too?”

The youth nodded.

“All of them?”

“All except Patrick, I suppose.”

“Patrick?”

“He’s on holiday in Ibiza.”

“Nice for him. When did he leave?”

“Six days back. Finished his shift at six and was in the air by eight.”

Fox looked at Clarke. Like him, she had done the arithmetic.

“So he was working here the day William Saunders was killed?” Fox checked.

“Suppose,” the youth agreed, eyes darting between the two detectives, Adam’s apple bobbing. “He’s not in any trouble, is he?”

“The officers you spoke to—they knew this, right?”

“I think I told them. Somebody would have.”

Fox nodded. But he was thinking: maybe, and maybe not. There was just a hint of dismay on Siobhan Clarke’s face—someone on her team might have screwed up.

“We need to talk to Patrick,” Fox was saying. “Do you have his number?”