Avinasi(Kamalhassan) is a motorcycle rider in the 'well of death' at a circus. He gets pulled into taking part in a kidnapping when his brother-in-law, the original member of the gang plotting the kidnapping, gets hurt. But the plan goes awry and Avinasi ends up kidnapping the wrong boy. The boy Daddu(Master Hardik) is the son of Ahalya(Manisha Koirala), a single mother and mistress of the ACP(Nasser). When Avinasi overhears the other gang members planning to kill the boy, he sets out to return the boy to his mother.

Contrary to Kamal's claims prior to the movie's release, Mumbai Xpress knows that its a comedy right from the start. The very nature of Pasupathy's kidnap plan(he is hooked to a crane and then flies over the city in plain sight before landing in a schoolyard to kidnap a student) makes this clear. But the plan is crazy enough to allow a lot of things to go wrong. And enough things do go wrong to keep us amused.

A noticeable aspect of Kamal's previous comedies has been the screenplay and the same is true here too. While the kidnapping is quite straightforward, the second half is all screenplay. The twists that lead to Kamal being mistaken for an undercover cop are handled smoothly and naturally and result in some of the funniest sequences in the film. The events that lead to confusion over who or what Mumbai Express refers to, have also been imaginatively thought up. And it is to the screenplay's credit that even offhand comments, like a horse's affinity for paper instead of grass, end up being important in the long run. But without 'Crazy' Mohan, his constant partner in previous comedies, Kamal's script fails to make full use of the situations thrown up by the screenplay. Laughs are definitely easy to come. But they rarely come solely out of the scipt. I am thinking hard but while I can remember funny sequences as a whole, I cannot remember any particularly funny bits of dialog.

Romance is given short shrift in the pursuit of comedy. Manisha's character is developed very poorly and we are never sure what her feelings or intentions are. Worse, since her character remains the same till the very end, she just doesn't seem like a good match for the honest and sincere hero. But one has to applaud Kamal's courage in the characterization of a Tamil cinema heroine. While even established directors(Vasanth) dealing with mature love stories( Rhythm ) resort to screenplay convolutions to ensure that their heroine is a virgin when marrying the hero, Kamal has as his heroine, an ex-bar dancer and mother to a 10-year old, who is now the mistress to a high-ranking police officer!

Rather than slowing to a smooth stop at the railway station, the movie stops abruptly like someone pulled the chain (with a name like Mumbai Xpress, I had to have atleast one train-related comparison!). In one scene we have Kamal fleeing from the police with his loot and in the next, we see everyone gathered together in harmony to celebrate his launch of a new project. The reels that capture what happened between the two events are probably lying on the cutting room floor somewhere (the fleeting glimpse of the two skimpily clad dancers gives us an idea why!).

With his experience, Kamal breezes through the role confidently. He has assembled his usual suspects together for the ride and they deliver. Pasupathy, in his first non-villainous role, gets the laughs by playing it straight. His exasperation at things not going according to plan is responsible for a major part of the laughs in the movie. Vaiyapuri gets a meaty role but doesn't bring anything extra to the table. Ramesh Arvind, in a different getup, gets the laughs with both his Telugu-laced lines and his money-hungry attitude. Nasser, with his pleading voice, is also very good while Manisha looks great but its not a memorable performance.

Both Kurangu Kaiyil Maalai... and Ele Nee Othi Po... play in the background and so require little or no special picturization. Vande Maataram..., whose off-key parts have been replaced by another song to avoid demeaning the National song, is the only number that is helped by the picturization since its both cleverly and hilariously picturized. Poo Poothadhu... is melodious and is picturized well. Shooting the film in a digital format results in a rather grainy look, especially in scenes that have 1 predominant color. The edges in some of the shots are also blurred.