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.
| Actor | Role |
|---|---|
 Karel FialaProfessor Oskar Grant | Professor Oskar Grant |
 Anny OndraAnny Grant | Anny Grant |
 Karel LamačIng. Milan Bell | Ing. Milan Bell |
 Jindřich LhotákDr. Karel Selín | Dr. Karel Selín |
 Emil Artur LongenDurk, the Magician | Durk, the Magician |
 Jan S. KolárFerdinand Kardan | Ferdinand Kardan |
 Přemysl PražskýMartin Bálek | Martin Bálek |
| AAntonín MarekBaron Evans Margus / Servant | Baron Evans Margus / Servant |
 Josef Šváb-MalostranskýJan | Jan |
| AAlfred BaštýřPresident of Police | President of Police |
| VVáclav PražskýReporter | Reporter |
| VVojtěch ZáhoříkGrant's Assistant | Grant's Assistant |
| JJindřich EdlHall | Hall |
| JJiřina JanderováSelín's Companion | Selín's Companion |
| JJosef BlažekGatekeeper | Gatekeeper |
| MMáša KolárováSeance Guest | Seance Guest |
| AAnna Lamačová-KarinskáSeance Guest | Seance Guest |