Strange envelopes marked with a crimson circle have started to appear across London: a series of blackmailing letters, each directed at prominent figures in society and communicating the threat of punishment if the demands within aren’t met—a promise that has yielded fatal results for those who have ignored those instructions.

Despite their best efforts, the police haven’t been able to track down this shadowy cabal of criminals, leaving them without the means to put an end to the terror that has overtaken London and its citizens.

The lead investigator in the Crimson Circle case, Chief Inspector Parr, finds an unlikely partner in Derrick Yale, an enigmatic detective with a peculiar gift for deduction, after the Circle claims its latest victim: Mr. James Beardmore, found dead in his estate after failing to pay £100,000.

The search for the killer and any leads that could help bring the Crimson Circle to justice is further complicated by the appearance of Thalia Drummond, a charming young secretary who’s more than she seems …

Published in 1922, The Crimson Circle became one of Edgar Wallace’s best-known works, and was adapted for film no less than four times.