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.
Karel Fiala
as Professor Oskar Grant
Anny Ondra
as Anny Grant
Karel Lamač
as Ing. Milan Bell
Jindřich Lhoták
as Dr. Karel Selín
Emil Artur Longen
as Durk, the Magician
Jan S. Kolár
as Ferdinand Kardan
Přemysl Pražský
as Martin Bálek
Antonín Marek
as Baron Evans Margus / Servant
Josef Šváb-Malostranský
as Jan
Alfred Baštýř
as President of Police
Václav Pražský
as Reporter
Vojtěch Záhořík
as Grant's Assistant
