Best known for The Thorn Birds, Australian Colleen McCullough is also the author of The October Horse and other titles in her Masters of Rome historical series. In her latest, she tackles Dean Koontz and Thomas Harris territory in a terrifying whodunit set at an Ivy League university.

Why did you take a break from historical fiction to write about a serial killer in On, Off?

For the last three years I have been going blind due to hemorrhages in both retinas. When the news of the blindness struck with my first hemorrhage, I racked my brains to think what kind of book I could write without needing to read huge amounts of background. The answer was the whodunit. I have the necessary tortuous mentality and obsessional traits all good whodunit writers must have.

Why did you set the novel in the 1960s?

Because my career at Yale Neurology started in the '60s and ended in the '70s. Therefore it was easy to deal with the inevitable medical/neurological details. I also thought it would be more fun to have a detective who groped through a fog, having few forensic tools [as they do today].

Were you influenced by a racially motivated crime of the period?

No, but I wanted the novel to reflect its era. I was privileged to live in the United States through the emergence of black militants. As an outsider, I was fascinated by the events of that time and well remember the trial of Bobby Seale, when New Haven was boarded up and closed down, and the National Guard rolled in. How could one write a book set in a small Connecticut city that was 80% black and not have African-Americans figure in it?

What's next?

At the moment I'm back in Rome, having decided that my giant novel (for so I regard the Roman books) was not complete until Octavianus was given the name of Augustus and both Mark Antony and Cleopatra were dead. I'm enjoying it, but when it's done, no more Rome.

You live on small Norfolk Island in the South Pacific. What's the crime rate?

After 160 years of the Pitcairn settlement on Norfolk Island without any crime more serious than the stealing of vegetables and tools, we had a murder in, I think, 2001. A girl was killed and the Australian Federal Police tried every way they knew to pin it on a local. Now, so long after, they have arrested a New Zealand man for it.