An American businessman finds himself racing through the bustling streets of India, only to arrive at the train station just as The Darjeeling Limited is departing. As he frantically attempts to catch it, a youthful figure named Peter Whitman, one of three brothers, successfully boards the train. This trio has not communicated in over a year, which followed the tragic death of their father in a car accident. The youngest brother, Jack, had been living in Europe, caught in a tumultuous relationship. Meanwhile, the eldest, Francis, has recently suffered injuries from a motorcycle accident that he later reveals is linked to a suicide attempt.
Francis summoned his brothers with the hope of mending their fractured bonds and embarking on a spiritual quest across India. Initial reunions are marked by forced happiness, yet the underlying distrust among the brothers quickly bubbled to the surface. Throughout this journey, the Whitman brothers indulge heavily in Indian prescription medications, with Francis often using his bandaged face as a pretext for his consumption. As tensions rise, Jack reveals to Peter his desire to leave early to reconnect with his ex, while Peter shares his anxiety about his wife, Alice, being seven months pregnant.
Conflict escalates when Francis criticizes Peter for having retained many of their father’s belongings, leading to even more resentment. Jack struggles with feelings of melancholia over his former girlfriend, while his brothers attempt to help him move on. Amidst this tumult, Jack becomes romantically involved with a charming stewardess named Rita.
On their meticulously planned trip, they visit a picturesque temple after perusing the local market where Jack buys a tear-gas gun and Peter, a small cobra. But their frustrations reach a climax when, upon entering the temple, Peter separates from Francis only to overhear Jack inadvertently divulge Peter's impending fatherhood. The return to the train proves chaotic as they discover the cobra has escaped, leading to hilarious panic.
As tensions flare in their cramped compartment, a physical altercation occurs, ending with Jack utilizing the tear gas, forcing them out. Their ensuing journey down a rural riverbank leads them to a heartbreaking incident where Peter tries to save a boy during a rafting mishap but is left devastated when the child drowns in the current.
They are later welcomed by villagers and invited to the child's funeral, leading to deeper reflections on their own father's funeral from the previous year. Here, the brothers bond over shared memories of grief and call into question familial relationships now more than ever. As they decide to abandon their pilgrimage and head home, a significant revelation comes when Peter learns he is expecting a son.
Their journey culminates at a convent where they confront their mother, Patricia, whose absence from their father’s funeral has long lingered in their hearts. Despite the absence of trust, the brothers pledge to lean on each other instead. As they return to catch their train, they drop their father's belongings in their pursuit, symbolically letting go of past grievances, and embrace a newfound camaraderie as they travel homeward together once again as brothers.
