Oscar de Muriel Books in Order

For the main arc: The Strings of Murder → A Fever of the Blood → A Mask of Shadows → The Loch of the Dead.
For the final stretch: The Darker Arts → The Dance of the Serpents → The Sign of the Devil.
For a quick sample: The Strings of Murder → A Fever of the Blood.
For the extras: The Hunt → The Falling Shroud.

Oscar de Muriel was born in Mexico City in 1983, in a building he likes to point out is now home to Ripley's Believe It or Not. He grew up in Mexico City, and his earliest stories were already full of claws, danger, and dramatic timing.

Dinosaurs came first.

At seven, he wrote and illustrated a tiny adventure about a triceratops and a stegosaurus fighting a hungry T. rex. A few years later, Michael Crichton's Jurassic Park scared him so much that it also showed him what a novel could do. The fear worked. He wanted to write.

The route to fiction was not a straight line. De Muriel moved to the United Kingdom to complete a PhD in chemistry, worked as a translator, wrote academic papers, and kept playing the violin. That mix of science, language, and music later became useful on the page. His mysteries often care about how things work: a poison, a locked room, a superstition, a violin string, a medical rumour that might have a rational root.

The idea that became Frey & McGray grew during visits to Edinburgh. The city gave him the right weather, the right stone, and the right amount of unease. Over pizza with friends, the figure of Adolphus 'Nine-Nails' McGray started to take shape: a rough Scottish detective with a damaged family past and a taste for occult explanations.

Then Ian Frey arrived to annoy him.

The Strings of Murder, published in 2015, set the pattern. A polished London inspector is sent north in 1888 to investigate a violinist's impossible murder, and he is paired with McGray, who runs a tiny police unit for cases that look ghostly, cursed, or just too strange for ordinary paperwork. Readers tend to come for the gothic setups and stay for the bickering partnership.

The later Frey & McGray books widen the canvas without losing that odd-couple engine. A Fever of the Blood heads toward Pendle Hill and witch lore. A Mask of Shadows folds theatre history, Macbeth, and Bram Stoker into the case. The Darker Arts turns a deadly séance into a test of loyalty, evidence, and nerves. Across the series, de Muriel keeps returning to the same useful question: what if the supernatural explanation is wrong, but still tells you something true about fear?

That mix suits him.

He has also written the Spanish-language Muerte en San Jerónimo books, beginning with Muerte en San Jerónimo, which move the mystery game to colonial Mexico and put Sor Juana Inés de la Cruz near the center of the action. Those books let him use Mexican history, convent life, class, race, food, and poetry in a different kind of detective story.

These days, de Muriel divides his time between northern England and Mexico City. He has lived in a former dairy farm near Pendle Hill, which feels almost too convenient for a writer of gothic mysteries, but in his case it fits. His books work best when the setting feels like more than scenery. It becomes part of the puzzle.