The infamous --- and real-life --- opium-eater Thomas De Quincey and his daughter, Emily, return in this final installment of David Morrell’s historical mystery trilogy.

By now, the mid-1800s, railroads have seen an acceleration in their popularity and thousands of miles of track have been laid across England. Previously unimagined travel speeds have freed people to not only move about more easily but live further from population hubs, like London. So when a gruesome murder occurs on the line leading to a community just a 20-minute ride from the city, panic ensues, making passengers wary and scarce. As it happens, De Quincey and Emily are in the adjoining compartment and hear the violent commotion. But for safety reasons, the compartments are always locked before the trains start moving, so there is nothing they can do until the train guard comes by with the key. By then, the killer has escaped.

"RULER OF THE NIGHT concludes a stunning series in which two unconventional sleuths go about solving cases during the Victorian era..."

De Quincey and Emily have a message dispatched to London Detective Inspector Ryan and Detective Sergeant Becker (each of whom is smitten with the young lady, despite her unorthodox ways --- or maybe because of them). While waiting for the authorities to arrive, Emily and her father do what little investigating they can. By now, De Quincey is suffering a bit more than usual, for his doctor has him reducing his intake of laudanum, which causes debilitating withdrawal pangs, so Emily shoulders much of the burden. But they soon find help from a surprise source, a figure from deep in De Quincey’s past. Carolyn, who he last saw the day he lost his beloved Ann those many years ago, resides just around the corner from Lord Palmerston’s house, where he and Emily are staying. In fact, his quest to discover what happened to Ann is what brought him back to London. Maybe Carolyn has some answers about their fateful parting. But does she also have some connection to the murdered man?

When another railway tragedy occurs, rumors begin to circulate that the Russians might be behind a sabotage plot, a not-unreasonable explanation given the war currently raging. But is that too convenient an excuse? Maybe someone wants detectives to think that, to distract suspicion from the real killer. Flushing the killer out proves to be tricky, though, and very deadly. And whether Carolyn knew the murdered man may turn out to be not so important after all, as the victim’s profession put him in contact with many well-off Londoners, lengthening the list of suspects remarkably. As the detectives get a brief glimpse at the dead man’s files, Ryan and Becker recognize many of the names they see, leaving them overwhelmed by the number who may have had a motive to kill. So far, though, that motive remains elusive.

RULER OF THE NIGHT concludes a stunning series in which two unconventional sleuths go about solving cases during the Victorian era, a time without cell phones and modern forensics, a time when they must rely on cleverness and logic, tenacity and the invaluable help of Scotland Yard. Removing the technology of today from their cache of resources makes it that much more challenging for them and that much more enjoyable for the reader in that it heightens the need for the characters to brainstorm.