Long ago, in a distant land, I, Aku, the shape shfiting Master of Darkness, unleashed an unspeakable evil. But a foolish samurai warrior wielding a magic sword stepped forward to oppose me. Before the final blow was struck, I tore open a portal in time and flung him into the future, where my evil is law. Now, the fool seeks to return to the past and undo the future that is Aku!

This cartoon from Dexter's Labratory creator Genndy Tartakovsky tells the story of a great warrior displaced to the distant future by the evil shape-shifting wizard Aku. The world has become a bleak place under the rule of Aku, segregated into fantastic tribes and ruled by Aku's evil robot warlords. Jack travels this foreign landscape in search of a time portal that can return him to his home time so he can "undo the future that is Aku!".