British writer M.R.C. Kasasian’s debut, The Mangle Street Murders, pits a detective duo, Sidney Grice and his female partner, March Middleton, against the perils of Victorian London.

So-called penny dreadfuls—the sensational crime accounts of the period—appear in the book several times. Did such publications inspire the novel?

When I was about 14, my parents gave me ’Orrible Murder, a book of illustrations from those penny dreadful magazines. I was fascinated by the drawings of policemen bending with lanterns over corpses in alleys, bystanders throwing up their hands in horror, people being stabbed or strangled in theatrical poses. The Victorians reveled in a good gruesome murder. I wanted to write a good old-fashioned murder mystery.

Sly hints suggest that Sidney Grice is a prototype for Sherlock Holmes.

It’s impossible to write a Victorian detective story without at least a nod to Sherlock Holmes. He’s still such a towering figure. I wondered how a real private detective would have felt about him at the time, especially if the living man found his own work thinly disguised in a Holmes adventure. In a later book, Sidney Grice confronts Conan Doyle on this very subject.

Unlike Holmes and Watson, Grice and Middleton are evenly matched, making for some memorable sparring. Was their equality of wits part of your conception from the start?

An infallible Grice would be unbelievable and tedious, just as an unintelligent March would be irritating. They both have their strengths and weaknesses. He is logical and observant, but can’t empathize with people. I wanted to create an equal for him, not just an adoring audience for Grice’s genius. March has crossed the world to India and Afghanistan, assisted in awful surgical procedures, loved and lost in terrible circumstances. She has a ready wit and a mind of her own. I absolutely love March. If I didn’t, I think it would show.

The voice of the novel is playful, but what it narrates—including the execution of an innocent man—is often quite dark.

Victorian London was a mass of contrasts. It governed one-fifth of the world’s population, but huge areas of the metropolis had little rule of law, and the justice system could be arbitrarily savage. Until the Criminal Evidence act of 1898, it wasn’t usual for an accused person to be allowed even to give evidence on his or her own behalf; executions were carried out quickly, offering little time for appeal. However, The Mangle Street Murders is primarily an entertainment. I wanted to evoke some of the flavor of the time without depressing readers.