You think that’s possible? That people would kill like that just because someone told them to?

Natural Causes by Fife farmer-turned-author James Oswald is the first in the Inspector McLean series. It is published by Penguin, rrp, £7.99. Bury Them Deep, the latest in the series, is published by Headline in February, rrp £14.99.

Other things lurked in dark corners. Sinister when glimpsed through the corner of your eye, they turned out to be perfectly innocent items when given full attention. A coat stand with a bowler hat, greatcoat and umbrella had been a dark assassin; the artfully discarded stole on the back of the moth-eaten high-back leather armchair had been a living fox, a witch’s familiar fixing him with an evil eye.

McLean blinked, and the stole blinked back, then yawned a great fang-baring snarl, stretched and leapt from the chair on to the floor.

Not a fox, but a cat, thin as a toast rack and with a tail that curved like a great shaggy question mark as it stalked across the room to inspect the new intruders.

“So, Detective Inspector McLean, Detective Constable MacBride.

“You want to know about human sacrifice, why people might try to do it, that sort of thing?”

Madame Rose pulled a pair of pince-nez out of her décolletage, where they had been hanging from a silver chain, and pushed them onto her nose.

“Pretty much. I’m trying to get a handle on a particular ritual. We think there was probably more than one person involved.”

“Oh there usually is. Otherwise it’s just attentionseeking.”

Solitary

“I meant more than one killer, actually. Six, possibly.”

McLean outlined what they had found in the walled-up basement, keeping the details as sparse as possible.

“Six?” Madame Rose leant forward in her chair. “That’s . . . unusual. Mostly it’s a solitary affair. Two people if you include the victim.

“The kind of people who go in for ritual killing don’t socialise well, you understand.”

“Why do they do it?” MacBride asked. McLean hadn’t actually told the constable not to say anything, so he tried not to let his annoyance show.

“A very pertinent question, young man,” Madame Rose said. “Some have speculated that it gives them a sense of importance lacking in their everyday lives.

“Others suggest that childhood experiences, usually violent and at the hands of close family members, cause the individual to conflate attention with love and thus mete out their own love accordingly.

“Many come from a strict religious upbringing where the child has not been spared the rod. Ritual is important to them, as is its subversion.

“For myself I think they mostly do it because they’re bonkers.”

“You don’t believe it works, I take it,” McLean said. “Oh, but of course I do. And so did your six madmen. Well, they must have done or they wouldn’t have killed the girl.

“Or at least one of them must have believed, and had the other five completely in his thrall.”

“You think that’s possible? That people would kill like that just because someone told them to?”

“Of course. If the leader’s charismatic enough. Look at Waco, Jonestown, Al Qaeda. Most cult followers don’t really believe what they’re being peddled. They just want to be told what to do. It’s easier that way.”

OK. Not quite what he’d been expecting when he’d come here. “So this ritual isn’t anything special, then. It could just be any random nutter with a god delusion.”

“I didn’t say that, inspector.” Madame Rose reached for a book that looked like it had only recently been fetched from the shelves to her desk.

Protection

She flicked it open at a page already marked. “Six organs, six artefacts, six names. Arranged at the cardinal points around the body. Tell me, were there markings on the floor? A circle of protection, perhaps?”

She spun the book around, showing the page to McLean. It was a crude black and white line drawing, done in a medieval style, showing a female figure lying with her arms and legs splayed.

A slit opened up her torso with nothing but black ink inside. All around her, a twining circle of vines twisted together, clumping in knots at her hands, feet, head and the space between her legs.

Beneath the picture were etched the words “Opus Diaboli”. McLean pulled the book towards him, but Madame Rose tweaked it away.

“That’s 17th Century. Probably worth more than your young constable here earns in a year.” “Where did you get it?” McLean asked. “Interesting choice of question, inspector.” Madame Rose ran a careful finger across the page. “I bought it from an antiquarian book dealer down on the Royal Mile. Many, many years ago.

“I believe he acquired it and several others from the estate of the late Albert Farquhar. Quite the occult enthusiast was Bertie Farquhar, or so I’ve heard.”

Another piece in the puzzle.

“And what is the ritual supposed to do?” “That’s where it gets interesting.” Madame Rose slid her finger under the page, turning it carefully over before handing the book back.

McLean looked at a new chapter, momentarily confused by the elegantly illuminated dropped capital. Then he noticed the ragged edge of a page torn out. The frayed edges were not fresh.

“It was like that when I bought it, in case you were wondering.” Madame Rose took the book back, carefully closed it and laid it back down on the desk, patting the cover like a good pet.

“I’ve spent the last 20 years looking for another copy.”

“So you’ve no idea what that . . .” McLean waved a hand at the book and the grisly image it contained. “What it was supposed to achieve.”

“‘Opus Diaboli’, inspector. The work of the devil.” It wasn’t until he stepped out on to the street that McLean realised it had been cold in Madame Rose’s study. Shade from being on the north side of the building, perhaps, but it felt more than that.

Dimension

As if the place lived in its own dimension. He looked back at the door, but the sign still said “palms read, tarots, fortunes told”.

The stone-work was still dirty, the window sill rotting away for want of a lick of paint. He shook his head, a judder passing through his body as it adjusted to the warmth of the sun.

“She was a bit weird.” DC MacBride stated the obvious. “And some.”

McLean shoved his hands in his trouser pockets as they started the walk back to the station. “But I think it would probably be fairer to say he.”

“He?” MacBride took three more strides. Turned to face McLean. “You mean she was a . . . He was a . . .”

“You don’t often see an Adam’s apple like that on a woman, Stuart. Or hands that big. I’d wager that ample bosom owed more to padding than nature, too.”

“So Madame Rose really is a charlatan. In more ways than one.”

“Oh, I wouldn’t knock the old fortune-telling. Anyone fool enough to part with their money for that sort of thing deserves to be poorer, if you want my opinion.

“And she . . . he has helped us, after all.”

More tomorrow.