The Unknown Purple.

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.