"The Adventure of the Red Circle" is one of the 56 Sherlock Holmes short stories written by Arthur Conan Doyle.

A youngish, heavily bearded man, who spoke good but accented English, came to her and offered double her usual rent on the condition that he get the room on his own terms.

After the landlady leaves, Holmes remarks to Dr. Watson that it seems likely that the person in Mrs. Warren's house is not the bearded man who made the arrangements.

Holmes and Watson go to Mrs. Warren's house and spy on the lodger, who they discover to be a young woman with a dark complexion.

She confirms that the Luccas were seeking refuge from the dangerous Giuseppe Gorgiano, who was out to kill Gennaro for betraying the Red Circle, a secret Italian criminal organization that they had both been involved in.

[7] The radio adaptation, starring Basil Rathbone and Nigel Bruce, was titled "Mrs. Warren's Lodger" and aired on 7 December 1941, the day of the Japanese attack on Pearl Harbor.

The East Coast broadcast was interrupted by a radio announcement that President Franklin D. Roosevelt would be addressing the nation at noon the following day.