The story of Blackmail revolves around the life of three people Dev (Irrfan Khan) – an honest husband, Reena (Kriti Kulhari) – the cheating wife and Ranjit (Arunoday Singh) – lover of the cheating wife. It all starts when Dev gets to know his wife is cheating on him with someone else. He goes through three options mentally – killing the wife, killing the lover or blackmailing the lover.
Dev goes with the third option that results in rise of innumerous unexpected situations. Rest of the story is divided into 4 blackmails taking place in the film. Who blackmails who, blackmailer becomes blackmailee and many more things get uncovered in the second half.