Young siblings Rocky, Colt and Tum Tum Douglas arrive for their summer stay with their Ninjutsu master grandpa, who has passed down his vast knowledge of martial arts. But they're accosted by the criminal Snyder, a rogue ex-student of Grandpa's who kidnaps the boys as part of a scheme to get to their FBI agent dad, Sam. But Snyder doesn't know just how skilled his abductees are!
