Young Lundi finds an amnesiac girl, names her Jeudi. A Count kidnaps her, mistaking her for a past love. Lundi rescues Jeudi and they seek her identity, aided by Leonhardt, while evading the Count and Nazis during WWII.

Lundi is young boy who lives in Switzerland in the late 1930s. One day while walking through the Swiss countryside, he finds a little girl who has lost her all her memories and does not know who she is. Lundi names her Jeudi and the two live happily together until one day a French count kidnaps Jeudi because she reminds him of a beautiful woman who rejected his love. Lundi rescues Jeudi, and they set on a journey to find her past. This journey leads them to a young musician named Leonhardt, who has clues regarding who Jeudi was before. Meanwhile they must escape from the Count Gourmont and the Nazis in the midst of World War II.