The ageing Baculus has accidentally shot a deer belonging to Count Eberbach, for whom he works as a schoolmaster.
When he is summoned to account for his actions, his fiancée Gretchen offers to intercede, but Baculus is reluctant to let her near the lecherous count. Her place is taken by a "student" (in reality the count's disguised sister, whom he has not seen since they were children) who offers to impersonate Gretchen. The count arrives in a hunting party with his friend the baron. He is so taken by "Gretchen" that he invites her and her friends to his birthday celebrations the next day.
At the castle, the countess gets into a misunderstanding with the baron, not realizing that he is her brother whom she too has not seen since childhood. Baculus arrives with "Gretchen", who is greatly admired by all the men, not least the count (who attempts to seduce her) and the baron (his brother-in-law) who proposes marriage. The count's game of billiards with the baron degenerates into farce as each tries to outdo the other in vying for "Gretchen's" attentions. To protect the girl the countess takes her under her wing. The baron then offers Baculus 5000 thalers if he will give up his bride, an offer he agrees to in the belief that the baron is referring to the "real" Gretchen.
Baculus tries to persuade Gretchen to go along with the baron's offer, only to discover that the baron is interested in the counterfeit Gretchen. The baron is furious when the plot is revealed, but all is resolved when the "student" reveals that he/she is none other than Baroness Freimann. The count pardons Baculus (who had in fact shot his own donkey), who is reunited with his fiancée.