Versatile actor Samuthirakani has played a number of characters in movies, where he puts across a pertinent social message and Sangathalaivan follows in that vein. However, one of the big differences in this movie is Karunas, who has brought out his A-game, yet again! Sangathalaivan, directed by Manimaran, is based on the novel Thariyudan and also stars Ramya Subramaniam, Sunulakshmi, Jr. Balaiyya and Vikram Anand, among others!

Rangan (Karunas) is a textile factory worker, who has come out of his own family due to some differences with his father and works for a greedy boss (Marimuthu). Rangan is a docile person, who doesn't believe in any sort of violence but when an accident to one of his co-workers results in her losing her hand, he approaches the local labourers union leader, the revolutionary firebrand Sivalingam (Samuthirakani). A series of events results in Rangan going up against the textile mill owners, including his own boss. Sivalingam has earned himself a lot of foes, due to his straightforward nature and his intent of helping the oppressed labourers get a better life for themselves, especially their basic rights from their employers.

Meanwhile, Rangan finds out that his boss's relative and his co-worker (Sunulakshmi) likes him and reciprocates the feelings. Just as his life seems to be turning rosy, Rangan faces a series of issues and has to take over as the leader of the labourers union. Can he justify his position? Can he lead the working class? Can Rangan adapt to the Communist lifestyle preached by the Union? What happens to Sivalingam? Will Rangan's love survive these radical transformations? Watch Sangathalaivan for the answers!

The role of a radical and revolutionary Union Leader, seems tailormade for Samuthirakani and he aces it with ease. Karunas as Rangan has a whole gamut of emotions to showcase and he has done an exemplary job. The whole movie revolves around these two characters mainly and they have handled it well. Sunulakshmi also has gotten some very good screen presence and she performs well. Ramya Subramaniam, Vikram Anand, Jr. Balaiyya, and Bala Singh have all made the best use of the screen space they have been given, especially Ramya who scores well in a de-glam, earthy role! Some of the scenes and situations in the movie are hard-hitting and evoke a lot of questions.

However, the intensity that gets built-up has not been sustained throughout and the predictability factor comes as a big letdown. Director Manimaran seems to be highly taken up with the Communist idealogies and the movie turns into a propaganda video for this, after a while. Along the way, the sufferings of the labourers has been portrayed very realistically and is sure to make your heart go out to them. The music and cinematography are functional but the editing could have been far better and aided the movie to a vast extent, despite the runtime being a modest 2 hours and a few minutes only.

It is indeed intriguing as to why Sangathalaivan has been projected as a movie with Samuthirakani as the hero, when in fact the entire movie revolves around Karunas's character and he holds forte throughout!