A baleful limping man walks through Prague. He is Asmodeus (Juraj Herz), the fiend of lustfulness, entertaining himself by putting together by magic couples of lovers.
Two young boys, play hooky from school in order to explore an ultramodern world's fair. They take in the many marvelous scientific and industrial exhibits, obtain literature, eat food, and generally run amok.
Forced behind British lines by engine problems, the Red Baron camouflages his plane, swaps uniforms with a dead soldier, and, posing as a Belgian, makes his way to a hospital.