Inventor Peter Marchmont has discovered a purple light that renders the user invisible. On his release from prison, Marchmont, disguised as Victor Cromport, uses the light to revenge himself against his former wife, Jewel, and her partner, James Dawson, who framed him for theft. Making himself invisible, Marchmont gradually ruins Dawson. He so wins Jewel's confidence and love that she is willing to kill Dawson at Marchmont's request. Finally, Marchmont leaves the scheming couple to their own misery and marries Jewel's sister, Ruth Marsh.

Chick Williams, a prohibition gangster, rejoins his mob soon after being released from prison. When a policeman is murdered during a robbery, he falls under suspicion. The gangster took Joan, a policeman's daughter, to the theater, sneaked out during the intermission to commit the crime, then used her to support his alibi. The detective squad employs its most sophisticated and barbaric techniques, including planting an undercover agent in the gang, to bring him to justice.