Laal recounts his extraordinary life story to a woman passenger (Aaryaa Sharma) seated across from him on a train. Laal Singh Chaddha, portrayed by Aamir Khan, grows up in a small village near Pathankot with physical challenges, particularly weak legs. His mother, Mona Singh, is his pillar of support, instilling in him the belief that there is no task too great for him to tackle. Although Laal struggles with academics and faces barriers in gaining admission to the local missionary school, his mother's relentless effort to work as a maid at the principal's house ultimately secures his place.
At school, Laal forges a deep bond with Kareena Kapoor, who plays Rupa D'Souza, his only friend in life. As Laal experiences defining moments—like watching India triumph in the 1983 World Cup and witnessing pivotal historical events such as Operation Blue Star and the assassination of Indira Gandhi—he faces both joy and danger. To protect him from growing threats, including bullying at school, Laal's mother makes the heartbreaking decision to cut his hair.
As time passes, Laal and Rupa's lives evolve. Rupa's family struggles take a toll on her, and after her mother's death, Rupa moves in with her grandmother, bringing her closer to Laal. Their journey takes them to Hindu College in Delhi, where Laal participates in athletics while Rupa chases her dreams of modeling. Amid shifting societal landscapes marked by protests and riots, Laal eventually joins the Army, influenced by a family legacy of service. In the Army, he befriends Naga Chaitanya Akkineni as Balaraju 'Bala' Bodi, and the two discuss future business plans, but fate leads Laal to a traumatic experience during the Kargil War, leaving him with injuries yet earning commendations for bravery.
Despite Laal's steadfast affection for Rupa, her aspirations lead her into a dangerous liaison with a gangster. When Laal confronts this painful reality, Rupa insists that she has her own path, acknowledging their profound yet complicated love. Meanwhile, Laal's encounter with Mohammed, a soldier he saved during the war, alters his perspective on life and business. They create an undergarment company named after Rupa, which unexpectedly flourishes—a testament to Laal's ingenuity and perseverance.
As Laal navigates loss, including his mother’s death, he dedicates himself to cultivating the land she left behind. The reemergence of Rupa offers hope, but circumstances tear them apart again as she faces her own battles with the law. In the aftermath, Laal embarks on a nationwide running journey, initially perceived as a quest for meaning, but ultimately driven by an emotional need to escape his turmoil. After years of running, he stops, citing exhaustion and a desire to return home.
Upon his return, a wave of joy washes over Laal as he discovers Rupa has been writing to him and that he is now a father to her child, Aman. However, sorrow looms as Rupa's health declines. Laal’s dedication leads to their marriage, but tragedy strikes with Rupa's passing. Following her death, Laal takes Aman to attend the same school he once did, completing his poignant journey of love, loss, and the enduring bonds that shape our lives.
