What is Legend of Zelda spirit tracks about?

Answer 1

Spirit Tracks takes place at least one hundred years after the events of Phantom Hourglass, in the now-established land Link and Tetra originally set out to discover at the end of The Wind Waker Link is an apprentice engineer for the royal railroads, hoping to become a full fledged rail tycoon. He learns from Princess Zelda that Spirit Tracks, ethereal railroads which not only serve as transportation but also seal an evil force, that has started to disappear from the world. The tracks were used to seal the evil because it could not be killed, instead buried, deep beneath Hyrule. Whilst investigating the matter, Link and Princess Zelda are ambushed by Chancellor Cole, who hopes to revive the Demon King, harbinger of the sealed evil. Cole attacks Zelda and kidnaps her body in order to utilize her powers. Cole's attack, however, brings about an interesting after-effect: Zelda's spirit becomes separated from her body, and only Link is able to see her. She is forced to travel with Link as he attempts to restore the Spirit Tracks, stop Cole, and return Zelda to her body. Along the way, Zelda both rides atop the train with Link and also physically possesses Phantom Guardians to assist him.

From Wikipedia