In Edinburgh at the end of the 19th century, during an extremely cold winter, a suffering pregnant woman seeks out the woman known as the witch, Dr. Madeleine (voiced by Marie Vincent). Soon after, a frail baby is born into the world, but the little one's heart is frozen solid. To save him, Madeleine installs a mechanical heart. The child's birth mother disappears without a word, so Madeleine raises him as her own son and names him Jack (voiced by Mathias Malzieu). She warns Jack never to get angry, to avoid intense emotional fluctuations, and especially to avoid falling in love. Little Jack grows day by day. On his tenth birthday, he ventures into town for the first time to play and encounters the angel of his destiny. His mechanical heart malfunctions, emitting thick smoke—he knows he has fallen in love. From that day on, Jack is destined to embark on a journey in pursuit of love... This film is adapted from the original work by Mathias Malzieu.