The storyline of 'Mago-Digo-Dai' is about a police intelligence unit in which main investigators are Sergeant C. K. Perera and PC I. O. Aari. The film opens with a daring investigation conducted by these two.
With their timely interventions, they manage to prevent a number of crimes. But they also arrest two innocents at the end of all their investigations. It always happens that Amila and his friend Malith getting arrested by the police.
Minister's daughter is abducted and the investigation to find her is handed over to the two police officers. The heads of the police intelligence keep their full trust on them and provide all powers and also the facilities including a dog for their support.