There are still water spirits among us. One group lives in Prague, led by Mr. Wassermann, who is using his wife's family as servants. All they need is their old house near the river. But the house is to be demolished. They have to stop it. And the only way is to drown Dr. Mrácek, who is responsible for the demolition. But he falls in love with Wassermann's niece Jana. He changes to a fish, is mistaken for the water spirit from Germany, is drowned and revived again. The other problem is the flour with ears... and so on...