"The Adventure of the Red Circle" by Arthur Conan Doyle is a short story published in 1911. When a landlady seeks Holmes's help regarding her mysterious lodger who pays double rent but remains invisible, the detective uncovers a hidden woman in fear. Through coded candle signals and surveillance, Holmes and Watson become entangled in a dangerous case involving an Italian criminal organization, a vengeful assassin, and a couple desperately fleeing their violent past across continents. (This is an automatically generated summary.)