The Scotsman suddenly discovers Jack aboard a ship with his memory completely blanked out. Refusing to let Jack think he’s an ordinary commoner, the Scotsman sets out to discover what caused the samurai to suffer his amnesia – and stave off bounty hunters after a now defenseless Jack, having forgotten how to wield his sword.
Jack finds a booby-trapped labyrinth, in the center of which is a diamond which could send him back to his own time. But a mysterious stranger, who has also entered the maze, could put Jack’s plans in jeopardy.
Seeking to end their struggle, Aku proposes a one-on-one duel between him and Jack, with neither combatant using their magic abilities. Jack agrees, but Aku’s honesty is unclear.
When Jack hears rumors of a time portal being found in the underwater city of Oceanus, Jack sets out to the city and is welcomed by its Triceraquins, but is unprepared for a terrible surprise.
Jack infiltrates a rave party after witnessing the participants stage a riot in a nearby town. It turns out that the DJ is one of Aku’s servants, and has been using his music to hypnotize the local children into becoming his master’s slaves.
When Aku catches a cold and spreads it to Jack, Jack is accidentally infected with Aku’s evil. Jack desperately seeks out a cure before Aku’s essence transforms him into the monstrosity himself.
While investigating the destruction of several scattered villages, Jack learns that Aku’s new “ultra-bots” are responsible. Unable to destroy them, he receives assistance from an unexpected source: their creator.
Centuries ago, the demon Aku is accidentally released by Jack’s father, who receives a magic sword from the gods. Eventually, he uses the same sword to imprison Aku beneath the earth.
