Oru Naal Iravil is mostly a faithful remake of the Malayalam film Shutter. The protagonist, Sekar (Sathyaraj) is someone who has made it in life all by himself, toiling hard in Singapore. But he is also unfairly prejudiced and chauvinistic. He suspects his teenaged daughter of having an affair just because he sees her talking with her friends and fixes a rushed alliance, turning a deaf ear to the protest of his wife.

A drunken night with his friends lead to a moment when, out of temptation, he solicits a call girl (Anumol) he comes across on the road. He is helped by Soori (Varun), an auto driver, who does odd jobs for him in the hope that Sekar will get him a job in Singapore. They take the woman to the empty property that is part of Sekar's commercial shopping space, which is also adjacent to his home. Promising to return in some time, Soori leaves them there leaving the place locked. He meets Sethubharathi (Yugi Sethu), a down-on-luck filmmaker, who had left behind his bag (containing his new script) in his auto, but is caught by the cops for drunken driving and the duo is forced to spend the night at the police station.

Meanwhile, Sekar starts fretting over Soori's absence and with the day having dawned, finds himself trapped with the prostitute, and facing the prospect of being caught at any moment.

What's refreshing about Oru Naal Iravil is how it manages to keep us thrilled even with seemingly mundane events. The script is a crafty one, where even a single event can result in a domino effect on the lives of the characters. Soori's chance conversation with a pimp leads to a mention of it during a drunken session, and that tempts Sekar to seek the services of a call girl. And a harmless peg in an earlier scene leads to the characters finding themselves in difficult situations. It's a film where every moment is crucial to the plot and every scene is shaped by how it is edited, and we can see why editor Antony would have been attracted to make his directorial debut with this film. The interval block is an excellent example of this. We see a shutter being opened and the shot cuts to Sekar cowering in shame at being discovered, leaving us in the edge of our seats. But when the film resumes, we see what is finally happening, and leave a sigh of relief. Antony uses this technique quite often and after a time, it starts to feel manipulative, even though it is effective at times. The filmmaking never manages to build tension than what's inherently in the script. The performances, too, feel, just functional. Sathyaraj is the right fit for the role, but he is made to act slightly over the top and we never get emotionally attached to this character. Much to our chagrin, it is often the busy score that tries to inject tension into the scenes.

And some of the coincidences - like the relationship between the filmmaker and the call girl - are distinctly cinematic. The filmmaker character actually is a stand-in for the audience, and his travails come across as forced. Similarly, the resolutions are rather too convenient. The episode is a moment of revelation for Sekar (he not only learns about himself, but also about the people close to him), but it is hard to believe the muted reaction of his family member, who learns of his predicament. There is not even a confrontation! In the end, we come out feeling underwhelmed as the film never fulfills the promise of its premise.