During a championship baseball match, the three brothers hear that their grandfather in Japan is in trouble, and head out to help him, conceding the match. When they arrive in Japan, they must use all their powers to defend him against his ancient enemy, who has returned to exact revenge.

Rocky, Colt and TumTum must battle an evil wealthy toxic waste dumper in order to save a local Indian tribe and their friend Joe. The 3 Ninjas must help find Joe's father and find a secret disk that contains evidence that could stop the toxic landfill that is destroying the Indian community. However the town is owned by the rich man and he controls the police and even the mayor. They must fight a motorcycle gang and renegade cowboys in this non-stop ninja adventure.

A young cop, haunted by the murder of his entire family years earlier, is recruited by a shadowy organization to hunt down criminals who are beyond the reach of the law.

Each year, three brothers Samuel, Jeffrey and Michael Douglas visits their Japanese grandfather, Mori Shintaro whom the boys affectionately refer to as Grandpa, for the summer. Mori is a highly skilled in the fields of Martial arts and Ninjutsu, and for years he has trained the boys in his techniques. After an organized crime ring proves to be too much for the FBI, it's time for the 3 brother NINJAS! To use their martial arts skills, they team up to battle the crime ring and outwit some very persistent kidnappers!