Ganesh(Vishal) joins his medical college in the middle of the fourth year. His only aim is to complete his studies and become a doctor and so he shies away from all trouble in his new college. But he ends up saving Srimathi(Reema Sen), his teacher's daughter, from some goons who are chasing her and she wants to meet him. When she does meet him, she realizes who he is and why he has joined this college.

Like all movies in this genre, Thimiru too has a first half that is propelled along purely on suspense. As a bunch of goons search for Vishal or he talks to the police or the principal of his college talks about his past (all silenced ofcourse), we know that things are not what they seem. We've seen enough movies to know that Vishal has had a violent past and that he will his shed his non-violent cloak and explode at some point. So the anticipation keeps us hooked and involved in the film. But the film doesn't rely on this alone. Reema Sen's unabashed flirting with Vishal and Vadivelu's comedy serve as good fillers and some strong sequences(like the way Vishal saves Reema from the rowdies) keep the pace from flagging.

The sequence that unmasks the hero for who he is is invariably the best part of such movies. Baasha pretty much set the standard for these sequences and though Thimiru doesn't reach that level, it manages to present it in a crowd-pleasing manner. The build-up as we near the point is nicely done with the scene where his collegemates get a surprise, being the best. The unmasking is picturized in a whistle-inducing way and the suspense makes us look forward to the second half.

When a film starts the second half on such a high, it is difficult to maintain it and director Tarun Gopi has encountered the same problem here. An overload of fights and ill-timed, awkwardly-inserted song sequences are all that the second half provides. Shreya Reddy's character is unique and interesting but is just the means to an end. And the end here is Vishal's multiple encounters with the bad guys. It doesn't help that the villains, especially Manoj.K.Jayan, are insipid and uninteresting.

Vishal makes a convincing action hero and it is clear that action is his strong point. Reema, who usually gets noticed even in hero-centric films, is wasted here. She is on the sidelines all along and the director's way of getting her included in the proceedings is silly. So she doesn't get the chance to display the great chemistry she shared with Vishal in Chellame . Shreya Reddy, on the other hand, gets a meaty role that she digs her teeth into. She is terrific as the woman chasing Vishal and her expressions and body language create a believable obsessive person. Vadivelu, as always, raises a few chuckles as the hostel warden. Yuvan Shankar Raja's tunes aren't exactly memorable but fit the mood of the film. But his background score provides the energy needed for the action sequences.