In a brief episode based on history, Bow Street chief officer Jeremy Sturrock (The Pangersbourne Murders, etc.) recounts how he foiled the 1820 Thistlewood Conspiracy to assassinate Britain's leaders and overthrow the government. Sturrock's suspicions begin when he finds a dying man on his doorstep--a man who moments later is whisked away into the night. Was the moribund fellow trying to give Sturrock some message or warning? (He only got out a few enigmatic phrases before disappearing.) Is this incident connected to vague murmurings of imminent mayhem in the streets and pubs? So it seems--as Sturrock, though officially relieved of his duties by his oafish boss. sleuths, chats, finds several more corpses, is lured into an ambush or two, is imprisoned in the conspirators' hide-out. . .but escapes in time to lead the small counter-revolutionary force that will prevent a bomb from blowing up the Prime Minister and several others. Despite bits of ribaldry and slapstick (usually involving Sturrock's hapless coachman Jagger), this outing is less frolicsome than the best Jeffreys efforts--as well as less mysterious. But, for fanciers of foggy London atmosphere, jocular period badinage, and fictionalized historical footnotes: a sturdy, if talky, little work-up.