In a kingdom with a legend of giants and an ancient war, a young farm boy named Jack lives a modest life tending his uncle's land. One day, Jack goes to town to sell his horse and encounters a monk fleeing from the king's men. The monk hands Jack a pouch of mysterious beans as payment, warning him to guard them. Upon returning home, Jack's attempts to hide the beans accidentally result in one of them getting wet, causing a gigantic beanstalk to sprout and shoot up into the sky, taking with it the house and Princess Isabelle who was seeking shelter there.

News of the princess's disappearance reaches King Brahmwell, who promptly dispatches his brave knights, led by Elmont, along with Roderick, an advisor with ulterior motives, and Jack to climb the beanstalk and rescue Isabelle. They discover a world where giants, thought to be mythical, are very real and menacing, posing a grave danger not only to the princess but to the entire kingdom. As Jack navigates this perilous new landscape, he uncovers his own courage and resourcefulness. What unfolds next shifts the fate of the kingdom as ancient rivalries and heroic feats come into play, leading to an epic confrontation that tests loyalty and bravery.