A Shogun who grew paranoid as he became senile sent his ninjas to kill his samurai. They failed but did kill the samurai’s wife. The samurai swore to avenge the death of his wife and roams the countryside with his toddler son in search of vengeance.
Shogun Assassin is a 1980 jidaigeki film directed by Robert Houston. It was edited and compiled from the first two films in the Lone Wolf and Cub series, using 12 minutes of the first film, Lone Wolf and Cub: Sword of Vengeance, and most of Lone Wolf and Cub: Baby Cart at the River Styx, both released in 1972 and based on the long-running 1970s manga series Lone Wolf and Cub created by the writer Kazuo Koike and the artist Goseki Kojima.