The owner of a coal mining operation, falsely imprisoned for fratricide, takes a drug to make him invisible, despite its side effect: gradual madness.
Charlie Chan is sought out by Pamela Gray, a desperate young socialite whose brother Paul awaits execution for the murder of a weapons inventor. Pamela is convinced of his innocence.
Ventriloquist Jerry Morgan has failed with another love affair. The reason: when the relationship reaches the point when it is time to discuss marriage, his two dolls become mean and jealous. Morgan's dollmaker Papinek is a member of a spy ring who has stolen the secret plans for the top-secret Lafayette airplane. Since Morgan is leaving for Zurich the same night, he decides to hide the secret plan in the heads of the dolls.
