The joyful celebrations at the royal festivities are suddenly interrupted by a juggler's attempt to kill King Gregory. The astronomer Petr, who saves the king, is accepted into service for his deed. He teaches the beautiful princess Korunka to read the stars, but the monarch is not particularly fond of their budding love due to the young man's lowly origins. Three musicians try to help the two lovers with magic, and when Petr manages to save the king from death a second time, it seems that the astrologer's dream will come true and he will finally win the princess's hand. Instead of the expected reward, however, he is banished...