Japan, 1844. Lord Naritsugu Matsudaira, the Shogun's illegitimate brother, is rising to power - but when his tyranny runs rampant, secret plans are laid to end his reign and his life. Veteran samurai Shinzaemon Shimada (Koji Yakusho) is charged with assassinating Naritsugu and puts together a small band who agree to lay down their lives to ensure their nation's future. Facing danger and impossible odds, the 13 assassins set a trap for the sadistic Lord in a remote village... but an army of samurai dedicated to protecting Naritsugu now stand in their way.