You are driving on the road, following the traffic rules and yet, you meet with an accident because some other person chose to drive recklessly. Vil Ambu is based on a similar train of thought — our lives are decided not just by our own choices but also by the actions of others, who might not even realise the impact that their decisions are having on our lives.

The film revolves around two young men — Arul (Harish Kalyan) and Karthi (Sri). The two have different upbringings. Arul is your normal middle-class guy, with a father who wants him to be practical and choose a routine career even though he is passionate about photography. Karthi hails from a poor family and grows into a petty thief. In the first half, we see how events in Karthi's life affect Arul's life — his bike is smashed, he misses an interview, he is suspected for a drug peddler and worse, ends up in lock-up when he is lured by Siva (Harish Uthaman), a criminal, with promise of cash, unaware that he is planning a robbery. In the meantime, Karthi finds love when Poongodi (Samskruti), the school-going daughter of Sekar (Nandhakumar), a local politician, starts wooing him. But, Arul's descent into despair continues. He is released on bail but shame haunts him and he cannot find Siva, who has vanished into thin air, and who is his only chance of clearing his name. But Arul's actions start to have an impact on Karthi's life. His luck begins to run out after the love affair is discovered by Sekar. Soon, the couple are on the run, but the lives of Karthi and Arul are once again intertwined. Can the two come out of their problems?

This is an interesting premise and there are elements that work well. In a normal film involving two heroes, we always get to a point where their lives crisscross, but here that doesn't happen. Arul and Karthi are blissfully unaware of the other's existence. The characters are also well-written and performed impressively by both Harish Kalyan and Sri. Debutant director Ramesh Subramanian also manages to sustain the tension in this tale and we care about the fate of these characters. There is also some laughter, courtesy Yogi Babu, who is turning out to be the new-age Senthil.

But the director doesn't take full advantage of the novelty of the premise. We get sub-plots that are routine (the friction between Arul and his father) and unnecessary (Sekar feeding off the rivalry between two of his party leaders), coincidences that become too much to take after a point (the all-too convenient climax, for example), and romantic tracks that stretch patience and plausibility (one, between Arul and Nithya (Srushti), his college mate, and the other between Arul and Kanagu (Chandini), a slum-dweller). He even contradicts the entire premise of the film when a character remarks that it is God who writes the destiny of the good while the bad write their own fate. It is this lack of conviction that pulls down Vil Ambu despite its lofty ambitions.