Professor Grant signs a contract with Dr. Selin for the sale of his invention of cold light with the plans for his invention being kept in Grant's apartment. The negotiations are secretly heard by the illusionist Durk, who wants to seize the invention. A few days later Selín is found dead, killed by a light bulb filled with poisonous gas. Durk performs at the birthday party of Grant's daughter Anna and seizes the plans for the invention.

Directors: Jan S. Kolár, Karel Lamač