As The Special Dead, Lin Anderson’s tenth book to feature Scottish forensic investigator Dr Rhona MacLeod opens, a young man has picked up a red-haired girl on a night out. He’s looking for easy sex, but having a cat jump on your back as well as being tied to your new lover by a red cord isn’t most people’s idea of a normal hook-up. And waking up the next morning to find a bunch of creepy Barbie dolls in the next room – “blondes, brunettes, redheads, naked, eyes glinting” – suspended over the corpse of the girl you slept with, is something most of us would wish to avoid.

But this is exactly the situation Mark Howitt, son of a local QC, finds himself in. Afraid of what people will think, he leaves the scene, hoping he can deny any knowledge of ever having been there. He’s not guilty, but he knows that he’ll look it if anyone realises what he was up to.

Rhona MacLeod is the forensic expert assigned to this strange crime scene. Working alongside her old colleague, DS McNab, she is still recovering from the fallout of a previous case, referred to as the Stonewarrior investigation. Anderson lets unfinished business from previous novels bubble in the background of the Wiccan mystery that emerges from the mysterious dead girl found among the hanging dolls. It’s a move that rewards her fans, although it may be confusing to those discovering Macleod and company for the first time.

Anderson has clearly relished researching the culture of Wicca, which is not, as popular misconception would have it, a devil-worshipping religion. Neither is it harmful, despite the popular image of witches as poisonous hags that has been prevalent since the Middle Ages. Her treatment of the religion is fair and open minded, although she can’t resist a small scene near the end that plays on a few of these prejudices and jabs a little at horror story conventions to make the reader gently question the physical world that is MacLeod’s usual realm of inquiry. The benevolence of Wicca is evoked through characters noting on several occasions the Wiccan Rede of “An’ Ye Harm None, Do What Ye Will”. The sentiments will resonate strongly with crime fiction fans seeking their own natural justice within the narrative. As with these spells, mainstream procedural fiction has a habit of revisiting people’s actions and intent back upon them.

MacLeod’s journey into the world of rituals and spells provides the bulk of the novel’s investigative component, although we are never really in doubt that explanations for these crimes lie in the physical and psychological. Lust plays a large part in the plot, from McNab’s attraction to one of the Wiccan professors through to MacLeod’s love life and her complex relationship with long-term partner, Sean. In Wiccan magic the act of physical love unleashes powerful personal forces, and as the book unfolds it becomes clear that this is as much a psychological truth as a mystical one. Those worried that Anderson might be about to attempt a Fifty Shades Of Grey, however, should be reassured that despite some scenes of an adult nature, the sexual envelope isn’t pushed too far.

The author’s skill has always been in making sure that MacLeod’s investigations are scientifically plausible, and here she uses her experience to find a balance between the unsettling worlds of magic and the rational; the crimes may be bizarre, but the methods used to solve them would stand up in the real world.

MacLeod’s pragmatic professionalism is her defining trait here, putting her in sharp contrast to McNab, who seems one bad thought away from a breakdown. The supporting cast are for the most part drawn with empathy, although Howitt sometimes feels a little broadly sketched: he moves from being a Jack-the-Lad to a wide-eyed patsy rather too easily; a touch more moral ambiguity with his personality would have given the book more depth. Yet in keeping with the Wiccan Rede, there is something to be said for the idea of someone’s poor decisions reaping consequences, even when their only crime is narcissism and thoughtlessness.

Despite these minor criticisms, Anderson clearly knows what her readers want and how to keep them coming back for more. While those unfamiliar with Rhona MacLeod may benefit from reading previous books in the series first, long-time fans should be very happy with this latest tale, which mixes ongoing character development with an unusual, often unsettling, central mystery.

Lin Anderson is at the Edinburgh International Book Festival on August 20