Grammar school teacher Bláha hurts himself in pursuit of a red lizard, and is lying unconscious in the lonely house of Santrucek family. The postman, who found Bláha's coat and hat in the water, announces to everyone in town that the professor has drowned. But, the venerable citizens are at that moment more interested in the theatre group with the beautiful guest actress Eva Gazdová. They demand a change of repertoire and manage to persuade the theatre manager to have the group play the musical comedy The Red Lizard instead of an established play.

Leopold Kohák married a rich widow a long time ago and now has nothing to do compared to his energetic wife. He's growing old and troubled by the fact that he betrayed his first love Emča and his beloved river Sázava where he spent his childhood and youth. A visit from an old friend Lebeda brings it all back to him. After a nervous breakdown Leopold secretly visits his home instead of going to the spa. A wandering tramp suggest Leopold should bathe in the magical waters of the Sázava, and slowly his youth returns to him.