Sherlock Holmes and Dr. Watson look into reports that a huge, vicious hound has killed Lord Charles Baskerville and that Lord Henry Baskerville is the next to be killed.

The short story focuses on two anecdotal episodes about the Prussian King Frederick II. In the first episode, the monarch meets an invalid. In the second episode, Baron Warkotsch's servant informs the king that Kappel's master is committing treason against the Prussian king, which puts Frederick's life in grave danger.