It's 1890. Sherlock Holmes and Doctor Watson return to Baker Street after a night pursuing a vicious criminal. Inspector Lestrade is waiting for Holmes with a proposition of national importance.

Lestrade tells Holmes that a school of detection has been formed to train a new breed of modern investigators that will serve in Great Britain and the Empire. Most students will become police officers. Some, however, will become bodyguards and spies. Holmes begins instructing his decidedly curious assortment of students from home and abroad. He does so with his customary gusto and inventiveness.

Scotland Yard, in the main, allocates crimes to solve and Holmes mentors his students. Occasionally, he shadows them in disguise in order to assess or even directly test their abilities with creative scenarios he devises. Certain crimes investigated by the students might appear trivial, such as the re-positioning of an ornament atop a garden wall, yet it will transpire an assassin has moved the ornament to create good sightlines in order to commit murder with a sniper's rifle.

Other mysteries are considered outside the domain of the police. For example, the inexplicable disappearance of a stone gargoyle, which is linked to an ancient family curse. Or a man suffering from amnesia who discovers that not only has he acquired a secret life but also gained an implacable enemy, too. Holmes, with the ever- trustworthy Doctor Watson in his wake, is kept busy with his students' cases, ranging from minor to serious, sometimes rectifying their mistakes and saving them from a variety of disasters.