Before the First Dark Curse
Sometime in the past, Jack travels to Wonderland and saves people from a beast called the Jabberwock. As a reward, she is given a magic mushroom from a "wise old woman" as a gift. In one kingdom's castle in the Enchanted Forest, Jack is having a secret rendezvous with the prince, James in his bedroom. She is dressed in a garb of white lingerie, and as they kiss passionately, James' father, King George storms in and demands his son cease what he is doing; as the treasury of the kingdom is being run down due to his latest runs of dalliances. When King George mentions that a giant is loose in the kingdom, Jack wryly comments she would like a crack at the giant. Later, Jack and James encounter Anton in the woods near the castle, where he has been watching the people at a local tavern. Jack and James call Anton their friend. Jack gives Anton a piece of mushroom that she got from slaying a Jabberwocky and rescuing a village. She informs Anton it will shrink him down to human size. Anton eats the mushroom and is shrunk. He then joins Jack and James in the tavern, and James tells Jack to get Anton anything he needs. Jack tells Anton her real name is Jacqueline. Anton sees James arguing with a knight at the door, and asks Jack about it. Jack tells Anton that the coffers of the kingdom are low, and that money is owed to a neighboring kingdom. Anton mentions the magic beans, but retracts this and offers treasure instead. Jack thanks him in return and kisses him on the cheek.
Later, Jack and James come up the beanstalk, shocking Anton. Jack informs him and Arlo that they are there for the magic beans, and that they will fight and defeat the giants to get them. When Arlo informs them they will fight back, Jack draws her sword and attacks alongside James. Later, in the castle, Jack is busy dueling Arlo while James is busy grabbing treasure. Jack manages to stab Arlo with her poisoned blade and makes a run for it, but Arlo grabs her and stabs her in the back. Mortally wounded and falling to the floor, Jack asks James to help her. James coldly informs her he has a kingdom to run and leaves. Jack, in shock, dies on the floor alongside Arlo.
After the First Curse
Many years later, Hook mentions all the giants except for one were killed. Although he was aware of Jack's part in the slaying of the giants, he was not aware that Jack was a woman. He and Emma Swan stumble upon Jack's skeleton while searching for the enchanted compass. Emma later uses Jack's sword to threaten the giant.