Pattiyal movie revolves Kosi (Arya) and Selva (Bharath) who are contract killers working for a middleman with the ironic name of Sami (Cochin Haneefa). Koshy who is an unblinking man with nary a feeling for life. Selva who is a deaf and dumb and is equally intrepid.
Saroja (Padmapriya) who is a salesgirl at a garment company is an outgoing and sprightly girl and is a friend of both Kosi and Selva. She is in deeply in love with Kosi. however, has no time for such finer emotions.But Cupid strikes his comrade-in-crime Selvam who takes a liking to Sandhya (Pooja), who is a salesgirl in a medical shop.
Life takes a decisive turn when the duo are sent on a mission to bump off a businessman and politician Nachimuthu Gounder (Santhanabharathy). By now the killers are a bit tired of their wicked ways.
They decide that after this final assignment, they would give up crime and lead a new life. But the plot takes many a twist and turn.