In Edinburgh, Scotland 1874, Jack is born on the coldest day ever. Due to the extreme cold he is born with a frozen heart which will not beat. The attendant midwife Madeleine saves his life by replacing his heart with a fragile but working cuckoo clock. She then advises him of three rules to prevent his untimely death: he must never play with the hands of the clock, lose his temper, or fall in love. Jack’s mother, for reasons known only to her, quickly decides her child would be better raised by Madeleine and departs, leaving Jack. Madeleine, incapable of bearing children of her own, raises and loves him as her own.Jack and the Cuckoo-Clock Heart 2014.
On Jack’s tenth birthday, Madeleine repeats the three rules before taking him into town for the first time. He meets a girl in town named Miss Acacia and becomes infatuated with her. After starting school shortly afterward, he also meets Joe, a bully who is in love with Miss Acacia as well. Jealous, the older boy and his gang of students torment Jack for the next four years. During an assault from Joe, the cuckoo of Jack’s clock heart gouges Joe’s eye, and Jack runs home believing he had murdered Joe. Madeleine, believing Jack to be a fugitive, helps him to escape.
Jack only wants to see Miss Acacia again and eventually meets up with Georges Méliès, a magician attempting to operate an early film camera. Georges helps repair his heart and agrees to join Jack in the search for Miss Acacia. They proceed to Andalusia, Spain in search of her.
After a long journey they arrive at a circus in Andalusia. Jack finds Miss Acacia but Georges advises him against revealing his identity to her. He proceeds to befriend her and foolishly avoids sharing his feelings. She hints that her heart belongs to someone from her past. It turns out that Jack was that person from her past. Jack eventually finds a way to reveal himself and gives a key to Miss Acacia which can be used to wind his heart.