The plot follows a retired ninja warrior, now married to an American woman, moves to Los Angeles at his wife's request in order to begin a new life for their two sons.

At the insistence of his American-born wife, Aiko, Yokohama salaryman Akira Saito decides to immigrate from Japan to the United States to raise their two sons Takeshi and Tomoya.

Unbeknownst to his family, Akira is in fact a highly skilled ninja, who had faithfully protected the secrets of his temple minded by his adoptive father and sensei, Koga.

Akira's meditation on this matter is disrupted by an attack from Koga to encourage him to wipe the guilt from his mind before it kills him.

Koga makes him swear never to reveal their secrets, and gives him a ninja helmet as a gift, while reminding him he can never leave his shadows behind.

In Houston, the Saitos meet with Sam Green, the widowed owner of a closed restaurant and apartment that Akira and Aiko have bought.

Daly removes loose floor boards and puts a large white box underneath, containing the Van Adda necklace.

Seeing Sam Green's packed luggage in his car, Willie incorrectly surmises that he is skipping town with the jewels.

Ignoring the threat, Willie sneaks into the hospital and murders Aiko, but is stopped by Anderson and his men before he can also kill Tomoya.

He swears he will make Willie and his men pay for destroying their dreams by returning to the ninja shadow world.

Behind closed doors, he performs rituals that signify his return to the ways of ninjitsu, and, with a makeshift forge, he creates a new ninja-to sword blade.

They fight a protracted duel to the death until Willie ultimately winds up being pinned through his wrists by Akira to a long buzzsaw platform.

As they are leaving, they are approached by Anderson, who discusses the massacre, mentioning that it is rumoured that the assassin was a ninja and asks if they still exist.

[2] and Briggs praising Kosugi as "the best kung fu man since Bruce Lee" and ranked the film high on his 10-best list for 1986.