Plum,
Is it KAriyila KAatru pola? It has both M's and Rahman. Lal is an inspector and Big M is a cine director. Big M is murdered and Lal comes for investigation. Though the scenario you are describing is not matching, this seems to be the movie IMO since you said it is directed by Padmarajan. Rahman is the brother of Lal. This is one movie where both M's never had a Face to Face scene. Does it ring a bell?
Regards
Bookmarks