'Alex Pandian' is a fast-paced action thriller that begins with Alex Pandian (Karthi) and Divya (Anushka Shetty) jumping of a train in an attempt to escape the goons who are seeking to kill them.
Three days later, Alex enters Kaalayan's (Santhanam) house in a comic sequence of events. Meanwhile, Divya is receiving treatment whilst Alvin Martin (Milind Soman) and Dr. GKM (Suman) are in search for the two. Upon finding Alex and Divya, the goons chase them.
Kaalayan demands to know who Divya is. It just happens that Divya is the daughter of CM (Visu). Alex, a local thief, is asked to kidnap Divya for 3 days so that the CM would sign the papers which would allow Dr. GKM and Alvin Martin to distribute fake medicines with devastating side affects.
Alex brings her and keeps her as a hostage in a forest. On the 3rd day, as Alex is driving back, Divya explains the reason for why she was asked to be kidnapped and thus requests him to take her back to her father. Alex changes his mind and decides to save Divya. The film shifts back to the present and by now, Divya has fallen in love with Alex. As fate would have it, the goons arrive at their hiding place. The film ends with Alex killing the villains and reuniting with Divya.