Black movie deals with the underworld operations in Kochi City. Karikkamuri Shanmugham (Mammootty) who is a hit man and a contract killer. David Carlos Padaveedan (Lal) who is a lawyer who masterminds and controls the operations of the underworld in Kochi..
David and Shanmugham are friends and Shanmugham does whatever David asks him to do. As a child Shanmugham was picked up from the slums by the local secretary of the Marxist Party (Janardhanan) and put in an orphanage.
He grew up without any love and affection and turned out to be a real 'goonda'. He becomes a ruthless and cold blooded killer. As the story goes, Shanmugham was entrusted with the custody of a girl by the party secretary. It turns out to be that the girl is his own daughter.
A newly appointed police officer Ashok ( Rehman) tries his best to clean up the corrupt system in the city but is killed by Carlos. Such incidents involving innocent people gradually makes a change in Shanmugham.
The rest of the movie deals with the transformation of Shanmugham from a killer to a peaceful man. He ends up fighting with his own gang controlled by David Carlos Padaveedan and a good hearted City Police Commissioner (Babu Antony) helps him out in his ordeal.