一串悲凉的歌声诉说着蜘蛛城的历史预言。战国时期，处于密林围抱的蜘蛛城，地形复杂，敌军攻来此地，必然迷路，因此城主稳坐城楼，指挥若定，四面排出大将御敌，可保此城固若金汤。大将鹫津武时（三船敏郎 Toshiro Mifune 饰）和副将三木因为平叛得力，准备回城领赏。途中，二人阴错阳差走入了密林深处，偶遇一白发老妪弹琴吟唱。他们觉得此事蹊跷，怀疑是敌方故布疑阵，因此上前以武力逼其就范。但此人却预言鹫津将夺城主之位，三木之子也将继承大统，正当两人将信将疑之时，此人化作一道白光销声匿迹。此后，回到城中，鹫津做了北城城主，但念及预言，心有不甘，于是在妻子浅茅的怂恿下，弑君，自立为蜘蛛巢城城主，然而这才只是预言的开始……After securing a major victory on the battlefield, Taketoti Washizu and one of his commanders, Yoshiaki Miki, find themselves lost in the maze-like Spider's Web forest. They come across a spirit-like seer who tells them of their future: both have been promoted because of their victory that day; Washizu will someday be the Great Lord of the Spider's Web castle while Miki's son will someday rule as Great Lord as well. When they arrive at the castle, they learn that the first part of the prophecy is correct. Washizu has no desire to become Great Lord but his ambitious wife urges him to reconsider. When the current Great Lord makes a surprise visit to his garrison outpost, Washizu is again promoted to commander of his vanguard but his wife reminds him of the danger that comes with the position. As pressure mounts, Wahizu takes action leading to its inevitable conclusion.