A Study in Shadow. The London Cypher, #1

In a world where crime has evolved beyond fingerprints and alibis, Dr. John Watson returns from war to find a London he barely recognises - a city where the most dangerous criminals leave no physical trace, only digital shadows. When he meets the brilliant Sherlock Holmes, a detective who sees patterns in security footage and follows trails across the dark web, Watson is thrust into a new kind of investigation.
Together, they must stop a vigilante whose victims are tech moguls hiding terrible secrets, and whose methods blur the line between justice and revenge. As Holmes and Watson unravel a conspiracy that spans the digital and physical worlds, they discover that the greatest threat isn't a single criminal - it's an entire network of digital ghosts, and the game has only just begun.