1631 г. Шогунът е болен и скоро ще умре. Неговото място трябва да заеме, най-големият син на шогуна, принц Имитсу. По-малкият син на шогуна, принц Тоданага, подготвя заговор за завземане на властта. Тоданага подписва тайно споразумение с принц Тозама, че след смъртта на шогуна, с армия да превземе Едо. Старейшините на шогуната съответната планове, които биха могли да доведат до сътресения и препирни в страната.

As the Shogun lays dying, seventeen Iga clan ninja are sent to infiltrate the impenetrable fortress where his youngest son is preparing to storm Edo Castle and name himself Shogun by force of arms. They are to either steal the documents that will eventually give him lawful claim to rulership, or they are to assassinate him. But even before they reach the castle walls, they find their every move countered by a ruthless ninja hunter in the employ of the would-be usurper (Konoe), who not only knows their every tactic but knows the exact make-up of their team thanks to his own spies within Edo Castle. As the Iga Ninja fall one by one, the mission's success or complete failure--where failure will result in a bloody war of succession--comes to hinge on a single young and inexperienced ninja (Kotaro).

駿府城内に隠された謀叛連判状を狙う甲賀忍者十七人、それを迎え撃つ根来忍者との緊迫とサスペンスに満ちた三十日間の攻防戦を描く忍者アクション巨編。幕閣から密命を受けた伊賀三ノ組十七人の緻密な役割分担と、ダミー、囮という自己犠牲の下に目的を達成するチームプレーを、新鋭長谷川安人監督がリアリズム・タッチで描破、東映忍者路線を決定づけた忍者映画の傑作。