Roland West, who directed this mystery, also co-wrote the stage play on which it was based. Inventor Peter Marchmont (Henry B. Walthall) goes to prison for a crime committed by James Dawson (Stuart Holmes). While he is locked up he discovers that his wife, Jewel (Alice Lake), has been involved with Dawson, and he swears revenge. Released from prison, he disguises himself and takes on the name Victor Cromport. Having invented a purple light, which makes him invisible, he begins using this device to secretly ruin Dawson's life. The detectives are baffled by the goings on, and in the end Marchmont wins back Jewel's love. As part of his revenge, he forces her to live with Dawson, who she now hates. Instead, he settles down with Ruth Marsh (Helen Ferguson), the girl who has been taking care of his son.
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