‘Chennai Express’ is about a 40-year-old Punjabi man, who is on a mission to immerse his grandfather's ashes down South. Enroute he meets a young Tamilian girl who has eloped. Their lives entwine and his journey takes an altogether different route.
The movie starts off with Rahul Mithaiwala (Shahrukh Khan), a forty-year-old bachelor living in Mumbai. His parents died in a car accident when he was eight years old, so his grandparents raised him. His grandfather (Lekh Tandon) owns a chain of confectionery shops. Before his grandfather's 100th birthday celebration, two of Rahul's friends invite him to accompany them on a vacation in Goa, which he accepts. Rahul's grandfather dies on the eve of the celebration. His grandmother tells Rahul that his grandfather wanted his ashes to be divided into two parts—one of each to be immersed in the Ganges and Rameswaram. She asks Rahul to take the ashes to Rameswaram and disperse them. Reluctantly, he accepts her request but is also eager to attend the Goa trip. Rahul and his friends plan to dump the ashes at Goa but his grandmother wants to see him off, forcing Rahul to travel by train. He books a single ticket on the Chennai Express, planning to meet his friends along the way. However, Rahul forgets to take the ashes, and he almost misses the train when he returns to collect them. As he tries to leave the train, he notices a young woman running to board it. He helps her and four other people board the moving train, but the train leaves the station before he can get off.
Rahul tries to flirt with the woman, who starts communicating by singing parodies of Hindi film songs, and explains that the four men are trying to kidnap her. Rahul lends her his mobile phone so that she can contact her friends, but the men with her grab it and throw it from the train. Rahul is annoyed, but says nothing because the men are carrying weapons. Rahul tells the ticket inspector about them, but they push the inspector into a river below a bridge. Panicked, Rahul learns that the men are her cousins, and that her name is Meenalochni "Meena" Azhagusundaram (Deepika Padukone). She is fleeing from a forced marriage to Tangaballi (Nikitin Dheer). Her father, Durgeshwara Azhagusundaram (Sathyaraj) is a powerful headman of the local mafia in Tamil Nadu.
Meena takes Rahul to her father and introduces him as her lover. Tangaballi challenges Rahul to a duel that Rahul unknowingly accepts, due to his lack of knowledge in Tamil. On the night of the duel, Rahul escapes with the help of a local policeman, Shamsher (Mukesh Tiwari), but he ends up on a ship with Sri Lankan terrorists and smugglers. A gun battle ensues between the police force and the terrorists. When police officers investigate an arrested Rahul, he tells his story and ends up back in Komban. Surrounded by Azhagusundaram's sickle-wielding henchmen, Rahul pretends to take Meena hostage and escapes with her in her father's car, battling Azhagasundaram's men. When the car has a breakdown, Rahul and Meena quarrel and part ways. Rahul, not knowing which way to go, returns to Meena, who takes him to the Vidhamba village. Meena tells the villagers that they are a married couple who needs protection and rest. The villagers decide to help the two.
Meena then realises that she has fallen in love with Rahul. When Rahul plans to sneak away, she argues, not wanting to earn the villagers' distrust. Tangaballi catches Rahul as he tries to leave, but the villagers help them escape again. Meena persuades Rahul to disperse his grandfather's ashes and travels with him to Rameswaram, where they complete the rites. On their way back, Rahul realises that he has fallen in love with Meena, and does not tell her where they are going. He takes Meena back to her father and tries to make him understand and honour his daughter's wish. He also tells Meena that he loves her. Rahul tells Tangaballi and his goons that he is ready for the fight this time. In the fight that follows, Rahul is severely injured but emerges victorious. Meena's father and Tangaballi reform, accepting that the love of a common man like Rahul is bigger than their physical ability and political influence. Azhagusundaram allows Rahul to marry Meena. Rahul then leaves a message that love knows no regional or language barriers and that with a strong heart, there is no limit to what the common man can achieve.
This one is SRK doing his DDLJ work with a twist of Tamil tadka in it as the romance initiated travels through the road of trouble! This isn’t the 90s anymore and falling in love needs quite a lot of toiling now!