The secret formula for the world's most powerful explosive has been stolen from the U.S. government. William Brown, a clerk who aspires to be a detective, has just received his badge from some anonymous Midwestern agency, and manages to get himself embroiled in the intrigue.
When Rachel Stetherill's daughter marries a man of whom she disapproves, Rachel disowns her. Five years later her daughter, now widowed, is killed. Her young son comes under the influence of a professional safecracker and is soon on his way to becoming a hardened criminal. Twenty yeas later the Stetherill family lawyer learns that the infamous thief known as Ladyfingers bears a striking resemblance to Rachel's husband--and has fallen in love with Enid, Mrs. Stetherill's young ward. Complications ensue.
At a party thrown at the Metcalf estate, the Marquise D'Irancy's Sultana diamond disappears when the lights go out during a power failure. Suspected of the crime is William Kirkland, the wastrel son of the wealthy Kirkland family, but William's sister Diana comes to his defense. Aiding her in the investigation is Clamp, a wandering peddler.
Wade Hildreth is sent to New York from London to receive a diamond necklace for Lady Gwendolyn from the jeweler Arabin. A gang of crooks led by Pete Fielding, known as "The Shadow," plans to keep Hildreth from going to Arabin's until they have robbed the store. Actress Morn Light, whom the Shadow loves, agrees to entice Hildreth to her apartment to be imprisoned. When she warns Hildreth because she wants to avenge her father's death, which was caused by the Shadow, the Shadow overhears and captures them both.
A country girl and a foppish Englishman are to inherit an estate, and the terms say that it can't be divided: The two must get married, and if one refuses, then the other gets the entire estate. The girl schemes with her twin brother to trick the Englishman out of his part of the inheritance. The girl's corn-fed crush helps out, while the twins' father dreams of being force-fed dog sausage.