This tale is set during Leonardo da Vinci's time in Milan, when he worked for the city's disturbing Duke Lodovico Sforza. The series is named after Leonardo's 1485 painting, Lady with an Ermine. Its subject is Cecilia Gallerani, a mistress of the Duke. The story follows the fortunes of a foundling, Francesco who leaves his monastery home with his problematic pet ermine Galay. They meet Leonardo as he ponders the mechanics of flight. Together they conspire to fulfil Cecilia's metaphorical desire to fly (flee), using one of Leonardo's inventions.