Mumbai Xpress is a black comedy-drama that follows the events of the kidnapping carried out by three men – Avinash a.k.a. Mumbai Xpress (Kamal Hassan), his brother Pratima Kazmi and a deaf stuntman who performs daredevil on the bike. The three men plot to kidnap a son of a wealthy man named Kishore Mehta (Saurabh Shukla) to get a handsome ransom. Things go wrong when they accidentally kidnap the wrong boy. The boy turns out to be the illegitimate son of police inspector ACP S.P. Rao (Om Puri). The kidnapping is followed by humorous mix-ups and chaos in the midst of all confusion. Will the three men still be able to get the ransom or get caught because of the mix-up?