Annually, three brothers Samuel, Jeffrey and Michael Douglas visits their warrior, Mori Shintaro whom the boys refer to as Grandpa, for the summer. Mori is Ninjutsu and a arts, and he's coached the boys in his techniques. It's time to get the three brother NINJAS after a organized crime ring turns out to be a lot of to the FBI! To utilize their martial arts skills, they team up to fight with with the crime ring and out-wit some persistent kidnappers!