Edinburgh Twilight (Ian Hamilton Mysteries #1) by Carole Lawrence

As a new century approaches, Edinburgh is a city divided. The wealthy residents of New Town live in comfort, while Old Town’s cobblestone streets are clotted with criminals, prostitution, and poverty.

Detective Inspector Ian Hamilton is no stranger to Edinburgh’s darkest crimes. Scarred by the mysterious fire that killed his parents, he faces his toughest case yet when a young man is found strangled in Holyrood Park.

With little evidence aside from a strange playing card found on the body, Hamilton engages the help of his aunt, a gifted photographer, and George Pearson, a librarian with a shared interest in the criminal mind.

But the body count is rising ...