Margaret Holt has been secretly helping her crusading D.A. brother get information on crime boss "Schemer" Marko. When the mobster confronts the brave girl, she accidentally kills him in self-defense. Looking for a place to hide, she stumbles upon the mansion of Winthrop Clavering, an amateur criminologist. Margaret becomes the man's stenographer, but soon realizes that he is close to solving the mystery of Marko's murder. Margaret must prove her innocence before Clavering turns her over to the authorities.
Conspiracy was written by John Emerson, a multi-talented actor, playwright, and director who had been a protege of D.W. Griffith. It was first performed as a stage play at New York's Garrick Theatre from December 1912 to May 1914, and then filmed later that year with Emerson starring as Winthrop Clavering. Leading lady Bessie Love also got her start with Griffith, who cast her in his epic Intolerance (1916). She is best remembered for her role in the science fiction extravaganza The Lost World (1925) and her Academy Award nominated turn in The Broadway Melody (1929). Comic actor Ned Sparks is beloved for his fast-talking, sarcastic characters in classics such as Gold Diggers of 1933, 42nd Street (both 1933) and Imitation of Life (1934), as well as for providing the voices of Terrytoons' Heckle and Jeckle. He was only 47 when he played the geriatric Clavering. Director Christy Cabanne's close to 40-year career in Hollywood ranged from Shirley Temple's first feature, The Red-Haired Alibi (1932) to Universal "B" pictures like The Mummy's Hand (1940).