Shadow in Scarlet by A. F. Stewart

Did you think Holmes and Watson were the only pair of consulting detectives in London? Meet Heyward and Andersen, consulting detectives in a paranormal London you never imagined... a world of airships, mysteries, and monsters.

Elspeth Heyward has never met a mystery she didn't want to solve or a risk she wasn't willing to take. Always up for adventure, she is determined to be the best detective and monster hunter in London and outshine her avowed rival, Sherlock Holmes.

New to the detective world, Lars Andersen just wants to stay alive and out of trouble, even if he secretly enjoys their cases. But when your partner likes guns and danger, work can be hazardous. Thank heavens for a good glass of brandy and excellent pickled herring.

The Case: Hunt down a vampire stalking their client, the infamous thrall, Scarlett LeJeune. The investigation leads them across the city as they hunt their suspect, but can they find this...