In Harris’s A Study in Crimson: Sherlock Holmes 1942 (Pegasus Crime, June.), the sleuth hunts a vicious killer in WWII London.

How long have you been considering the idea of transporting Sherlock Holmes to WWII London?

In 2019, I was writing fictional adventures of Arthur Conan Doyle during his early teens. Writing a Holmes novel naturally crossed my mind, but what held me back was that there are already so many pastiches. It seemed to me that if I wrote one, no matter how good it was, it would pass unnoticed. One day, my eye glanced upon my boxed DVD set of the Rathbone movies and the idea struck me. Here was a version of Sherlock Holmes updated to the 1940s portrayed by the actor most identified with the character. To turn that concept into a novel seemed such a wonderful and fruitful idea, it was surprising that no one had thought of it before.

What about those films most appealed to you?

I have many happy memories of settling down with my wife and our sons to enjoy these films with a big pot of tea and a heap of biscuits. These are fast-paced thrillers and, very importantly, brand new Holmes adventures, even though they often made clever use of elements from the Conan Doyle stories. The transition from Rathbone and Bruce’s performances in the two Victorian-set movies that preceded Universal’s 1940s series into this new setting feels absolutely seamless. This is a tribute to the actors and to the quality of the scripts in which they always sound exactly like Holmes and Watson should.

What was the hardest part of those films to translate into a novel?

The most important decision I had to make before actually writing the novel was establishing a new timeline for the characters now that they were not from the Victorian era. The movies could just skip over that, but in a novel that background had to be provided. I started by making Holmes and Watson the same age as the actors so that, like Rathbone and Bruce, they both served bravely in WWI. This had to be crafted in such a way that these different life experiences would still lead to them being the beloved characters as described by Conan Doyle.

Are there limits to the settings Holmes can be plausibly placed in?

I think those who seek to carry Holmes onward in new ways in books, film, and television have a responsibility always to respect Conan Doyle’s original work. Our attachment to it is like a strong piece of elastic that we can stretch, but we should be careful not to let it snap.