The Portorican prime minister asks British detective Sherlock Holmes to find a twin for King Fernando XXIII, a weak and frightened man who fears anarchists and does not want to show himself in public. Holmes finds in the Czech newspapers a photo of the perfect double, František Lelíček, a daring bon vivant drowned in debt, so when Holmes offers him money, Lelíček decides to travel to Portorico and play the role.

Vlasta Burian
as František Lelíček / Fernando XXIII

Martin Frič
as Sherlock Holmes

Lída Baarová
as The Queen / Her Doppelganger

Theodor Pištěk
as Prime Minister Count Mendoza

Eva Jansenová
as Conchita

Fred Bulín
as James, Holmes' Butler

Arnold Reimann
as Cafe Owner

Jára Beneš
as Composer

George Andreani
as Composer

Robert Ford
as Conspirator