Each year, their Japanese grandfather, Mori Shintaro whom the boys refer to as Grandpa is visited by three brothers Samuel, Jeffrey and Michael Douglas, for the summer. Mori is an extremely skilled in the fields of Martial arts and Ninjutsu, and he's coached the boys into his techniques. After a organized crime ring turns out to be too much for the FBI, it's time to get the 3 brother NINJAS! To use their martial arts skills, they outwit some kidnappers and team up to battle with the offense ring!