At New Delhi Railway Station, Poochiappan, Dhanush, is a railway catering server on duty aboard the New Delhi–Chennai Express. He works with his team member and best friend, Karunakaran (as Vairam), under his supervisor, Thambi Ramaiah (as Chandrakanth). On the journey, he encounters Saroja, Keerthy Suresh, an aspiring singer who dreams of making it big, and who serves as the makeup artist for actress Srisha, Pooja Jhaveri. Poochi confesses his feelings for Saroja, and together with his friend, he hatches a plan to help her along the way. To bolster her confidence, Saroja is made to speak on the phone with Vairamuthu, a voice impersonated by Karunakaran in the role of the famed Tamil poet; the ruse is meant to boost her motivation, even though Saroja herself isn’t yet a strong singer. Despite this, Saroja remains close to Poochi, unaware that the Vairamuthu connection is a fabrication.
Their journey is shaken when the train reaches Jhansi Junction, where Union Minister Rengarajan, Radha Ravi, boards with two bodyguards. One of the bodyguards, Nandhakumar, clashes with Poochi and Saroja, and the minister publicly humiliates him, fueling a personal vendetta. Poochi pushes to secure an apology for Saroja, and the minister agrees to retrieve a gun he had lost, a gun Poochi later discovers is in the minister’s possession. The captain’s threats set off a dangerous escalation, as the minister vows to target Poochi and Saroja. Meanwhile, at Nagpur Junction, a separate disturbance unfolds as robbers secretly board the train, slipping past the crew.
The following morning, Srisha’s mother notices Saroja with Poochi and informs Srisha’s uncle, who demands that the truth be surfaced by contacting Vairamuthu. When the truth about Vairam is exposed, Srisha’s uncle chastises Saroja, who pleads with him not to show his face. In a tense confrontation, Nandhakumar corners the pair and locks the uncle away. A frightening sequence follows when the train derails into a dangerous situation after the engine is compromised—bulls on the track, miscommunications between the guard and the driver, and a misfired brake signal. The deputy driver’s green-flag signal leads the locomotive to accelerate, and Saroja finds herself racing toward danger as she attempts to board the speeding engine while the passenger cars tumble behind.
As the train hurtles forward, burglars strike and hijack attempts escalate the fear among the passengers. Poochi fights back, overpowering Nandhakumar and protecting Saroja, and he equips her with a walkie-talkie to stay connected. Nandhakumar dies in a collision with an oncoming rail tunnel, and news swirls that a terrorist attack has occurred. Authorities conclude the train is hijacked, but they soon realize the real threat is an out‑of‑control train rather than a formal hijack. Realizing they must act fast, planners turn to Poochi and Saroja for guidance on how to stop the train by triggering the emergency brakes. A short circuit foils the brakes, so the plan shifts to detaching the engine from the passenger cars. Poochi makes a perilous jump onto the locomotive to save Saroja, and she comes to recognize her feelings for him.
As the train nears Chennai Central, the station is evacuated, and panic subsides as the separated passenger compartments approach safely. The locomotive crashes into the station, leaving Poochi and Saroja injured but alive, while the passengers emerge unharmed. In the aftermath, the media interviews the duo, and Poochi is hailed as a national hero for saving countless lives. The harrowing journey—a blend of courage, misdirection, and heart—ends with a quiet realization between Poochi and Saroja, cementing their bond even as the world around them applauds their bravery.
