The multi-storey lab is a neuroscience research institute attached to Chubb University (geddit? McCullough was at Yale for ten years, working on epilepsy as a physiologist) and the first chapter gives us a giddy tour through the floors and personnel, and even their food choices, unappetising though they may be. I dutifully reread sections to come to grips with the parade of white-coated misfits, potential Nobel laureates, dominatrices, and clerks. More murders are revealed. More happen. The villain is clearly one of those attached to The Hug, the pet name for the institute. McCullough is, I suspect, taking more than a little revenge for the years she endured at Yale, where, at that time, women earned little and prospered less. That’s the period in her life when she turned to writing as a salvation. The Hug turns out to be a seething swamp of intrigue and perversity. But how could that explain the systematic torture and death of innocent girls, all pious, all straight-A students, all with shining prospects?

Our short Italian police lieutenant gets nowhere slowly. He struggles with the laboratory science – displayed effortlessly by our expert guide – and tracks and retracks the distinguished cast. Could it be the professor in charge, with his Cary Grant looks? Could it be Mistress Lash and her submissive Ken Doll playmate? What about the devious German, once photographed in Adolf Hitler’s company: could this be a Dr Mengele in disguise?

More bodies, more gore. Families are utterly distraught at their instant transformation from tranquillity and hope to despair and oblivion. The girls are conjured away without trace. The killer is clever and strong; he is also technically resourceful. A man is garrotted with wire. The door to our beanpole heroine’s rooms is opened by sawing through a steel bolt. She escapes by clambering, long legs extended almost impossibly, up the balconies of the apartment block. Forgive me: I had an irresistible picture of Popeye’s Olive Oyl scaling a brownstone like a spider up a drainpipe. She falls into the policeman’s arms. Love has awkward origins.

Why sixteen-year-olds? Why on such a regular timetable, precisely predictable by the calendar? How can someone have such enormous resources to dedicate to such an awful enterprise? How is every suspect able to present an ironclad alibi? Could there be two villains?

Just as intriguing is why Colleen McCullough, author of The Thorn Birds (1977), The First Man in Rome (1990), Caesar (1994), Roden Cutler VC (1998) and other well-received books, wanted to turn to crime at this point in her celebrated career. I can’t help wondering whether, other than wanting to exploit the Yale connection, the unsolved murder where McCullough lives on Norfolk Island gave her a prompt, not to say an inspiration. (This is covered in Tim Latham’s recent book of the scandal, Norfolk: Island of Secrets: The Mystery of Janelle Patton’s Death, which was reviewed in the previous issue of ABR.) She could hardly set her own mystery in Norfolk and then try to get on with the locals afterwards. Though, as McCullough told me in August, she would welcome coming back to Australia where she grew up (she stays because her husband is an Islander).

So, is On, Off worth the effort? In the end, yes, because McCullough is a formidable plotter. The dénouement is as unexpected and resonant as anything like that can be. The scientific detail is also satisfyingly dense and convincing. But for something with more human characters and rather less repulsive butchery I can’t go past two other Australian crime ladies: Jane Goodall and her beguiling second murder mystery The Visitor and Gabrielle Lord’s forensically rich Dirty Weekend. At least you’ll be able to swallow afterwards.