Three amateur thieves plot to kidnap the young son of wealthy Chettiar (Santhana Bharathi) from school. They do a trial run. However, on the eve of the kidnap, the guy whose job is to operate a crane in this plan is hospitalized. The services of Avinasi a.k.a. Mumbai Xpress (Kamal Haasan), brother of Kovai Sarala, a deaf stuntman performing daredevil bike acts, is roped in. Twists and turns take place where the other two gang members are hurt, and invariably, our Mumbai Xpress is left to perform the task all by himself. He kidnaps a wrong boy Daddu (Hardhik), the illegitimate son of Ahalya (Manisha Koirala) and police officer Rao (Nassar), but manages to get a huge ransom from Chettiar by default. A brawl takes place between the original kidnap planners - Chidambaram (Pasupathy), Johnson (Vaiyapuri), and Avinasi - in handling Ahalya's child, but Avinasi delivers the child unhurt to his mother.