Lanka derives its gist from the Hindi adage 'ghar ka bhedi lanka dhae' that comes from the Indian epic Ramayana, which implies how your most trusted allies could be the ones to betray you (like Raavan's brother Vibhishan denounced him in Ramayana). While this film could have gone down as another ordinary story, the Ramayana analogy moderately succeeds in giving it more character (though it judiciously employs merely three characters from the epic).
Jaswant Sisodia (Manoj Bajpayee) rules supreme in the town of Bijnor and one of his indulgences involve forcing a girl Anshu (Tia Bajpai) to be his mistress. Anshu's parents are as helpless and humiliated as the vulnerable victim, who ironically gets willfully raped every night by Jaswant. Jaswant's close aid (Arjan Bajwa), who he as well considers his younger brother, comes to the town and supervises his illicit operations. His loyalty towards Jaswant remains integral until his empathy towards Anshu overpowers it. That's when he decides to betray his mentor.
Visibly Tia symbolizes Sita, Manoj Bajpayee represents Raavan, and Arjan Bajwa stands for Vibhishan in this selective depiction of Ramayana. And through its dense drama, the film justifies Vibhishan's stand to stand against the morally wrong Raavan. Where debutante director Maqbool Khan's expertise comes is in giving Manoj Bajpayee's character a poised tone wherein, on one hand he is despicable for the heroine, on the other hand he is role model for the hero. As an audience, you relate to both the extreme shades in his personality, which can also be immensely attributed to Bajpayee's persuasive hold on the character.
The plotline isn't entirely inventive and one has seen thematically similar interpretations, notably in Rakesh Roshan's Koyla (1997) or more recently Kites (2010). How it steers clear from other cinematic adaptations of Ramayana is from the fact that it intentionally avoids incorporating Ram as the ideal protagonist and substitutes it with Vibhishan who might not be perfect yet opposes evil. So the entire essence of the film lies in the camaraderie between Raavan-Vibhishan (Bajpayee-Bajwa) and their subsequent conflict.
Thereby the director keeps the romance track between Arjan Bajwa and Tia Bajpai to the minimal and thankfully the narrative never branches out into their individual love story. A better alternative would have been to restrict their bonding only till empathetic emotions (like in Emraan Hashmi's Awaarapan) over the avoidable streak of romance.
The focus is more on the conflict between men than highlighting the trauma inflicted on the woman. Thereby the lust and obsession that fuels Jaswant's desire to dominate Anshu, both, physically and psychologically, remains peripheral to the plot and doesn't register effectively enough. In fact their back-story is never fleshed out. Somewhere there is more amity between the male leads than animosity with Arjan Bajwa's duty-bound character being a mute spectator for the major runtime before he rebels in the very end. And post his revolt, the film comes to a quick end with a solo climactic confrontation scene between the men. The climax, however, seems hurried and convenient in the bigger picture.
It's sad then that what could have been shown as a rare account of ethical unfaithfulness ends up being a generalized preachy epilogue on how men should treat woman with respect and how wronged woman should not lose hope and continue their fight against injustice and blah blah blah. It almost changes the tenor of the male-dominated drama to a woman-liberation film.