In 1861, Countess Angelina, ruler of Bergamo in North Italy near the Swiss border, marries Mario, a baron she has known since childhood. When the castle is threatened by Hungarian hussars led by Colonel Teglash on their wedding night, Mario flees.
At midnight, the paintings in the ancestral gallery come to life, and their subjects ask Francesca, Angelina's great-great-great-great-grandmother who looks exactly like Countess Angelina, to save the castle just as she did in the 16th century. Through a spyglass, Francesca observes Teglash leading the advancing army and finds herself attracted to him. When he sees her portrait, Teglash is puzzled by the fact she is wearing an ermine coat but no shoes.
Angelina greets Teglash, who flirts with her when he learns her bridegroom has escaped, but she makes it clear she respects her marriage vows and is concerned about her husband's safety. Angelina's servant Luigi, seeing how smitten the colonel is with his mistress, tells Teglash how three hundred years earlier, Francesca retained control of the castle when a tyrannical duke attempted to seize it. Via flashback, we see her, barefoot and in ermine, present herself to the duke and accompany him into his tent. After a period of time, Francesca departs, leaving the duke, with a dagger in his back, lying dead on his bed. Luigi tells the colonel that, according to rumor, she killed the duke because she feared she was falling in love with him.
Disguised as a gypsy, Mario returns to the castle but runs off when soldiers come to investigate. When he is captured, Teglash, unaware of his identity but impressed by his musical ability, decides to spare Mario's life and make him his personal gypsy. When he realizes he is Angelina's husband, he offers to free him if she dines with him that night, but she fails to rendezvous with him.
Francesca visits Teglash while he is asleep, prompting a dream in which Angelina joins him for dinner and demands a kiss. While she embraces him, she removes a knife from a roast pig and throws it at the clock, effectively stopping time. The two acknowledge their love and, as the gallery portraits look on, they fly up and crash through the roof.
The following morning, Teglash wakes to find the knife still in the pig and the clock ticking. Angelina arrives, and Teglash tells her he is freeing her husband and then describes his dream, touching her with his obvious deep feelings for her. When Mario arrives, she assures him she had nothing to do with the colonel.
Time passes, but Teglash still mourns the loss of Angelina. One night, while he is asleep, she arrives and falls asleep in a chair near his bed. Teglash revisits his prior dream, but this time the knife falls from the clock and Angelina stabs him with it. He awakens with a start and finds Angelina, who tells him Mario has left her and proposes they wed. That night at midnight, the portraits come to life once again to celebrate their union with song and dance.
