The story begins in the scenic hills of Ooty, where five boys—Gopal (Ajay Devgn), Madhav (Arshad Warsi), Laxman 1 (Shreyas Talpade), Laxman 2 (Kunal Khemu), and Lucky (Tusshar Kapoor)—reside in an orphanage managed by a businessman named Jamnadas. The group is divided by a mutual dislike; Gopal and Laxman 1 form one duo, while Madhav, Lucky, and Laxman 2 form a trio. Their personalities are distinct: Gopal lives in constant fear of ghosts, Lucky is mute, and Laxman 1 struggles with a lisp. During their time there, they are aware of the local librarian, Anna (Tabu), who possesses the supernatural ability to see spirits. One night, the boys discover an abandoned baby outside the orphanage and decide to take her in, naming her Khushi.
The friendship between the two groups is further strained when Madhav plays a prank to terrify Gopal inside an empty bungalow owned by Colonel Chauhan, a friend of Jamnadas. The resulting conflict leads to Gopal being punished, which sparks a chain of events where Gopal and Laxman 1 decide to leave the orphanage. Shortly after, Madhav, Lucky, and Laxman 2 also depart. In the aftermath, little Khushi is adopted.
Twenty-five years pass, and the five former orphans have grown up to become plot seizers. Gopal and Laxman 1 now work for Babli Bhai (Sanjay Mishra), while Madhav, Lucky, and Laxman 2 are employed by Vasooli Bhai (Mukesh Tiwari). Their paths cross once again upon learning of Jamnadas's passing. Returning to Ooty for the memorial service, they encounter Colonel Chauhan, who is now blind, as well as Anna and Pappi (Johnny Lever), a former orphan and caretaker who suffers from memory loss. They also meet Damini (Ashwini Kalsekar), the caretaker of the bungalow, and learn about the tragic demise of the Colonel's daughter.
During the memorial, a businessman named Vasu Reddy (Prakash Raj) reveals his cold-hearted plan to demolish the orphanage to make way for a new building. This creates tension, especially when Anna and the Colonel decide to rent out two rooms, much to Vasu's annoyance. After the group returns home, a supernatural event occurs: a ghost possesses Laxman 1 and speaks in a booming voice, claiming that Jamnadas's death was actually a murder, which leaves Gopal absolutely terrified.
In an attempt to help, Anna convinces Gopal and Laxman 1 to move into Colonel Chauhan's house. Meanwhile, the ghost possesses Madhav, influencing Vasooli Bhai to assign Madhav, Lucky, and Laxman 2 to evict Gopal and Laxman from the bungalow for Vasu's benefit. This manipulation effectively brings all five friends back to Ooty. Upon arriving, the two groups discover that the Colonel's daughter died on the same night as Jamnadas, yet their rivalry persists. Madhav and his crew attempt to scare Gopal away, but the ghost possesses Gopal, who then proceeds to beat up Lucky and Laxman 2.
The conflict escalates when Vasu orders Madhav's group to burn the house down. However, Lucky becomes possessed by the spirit, speaking in the same haunting voice and frightening everyone. Despite the chaos, Anna and Damini persuade the group to stay for a birthday celebration, leading to a heartfelt reconciliation. However, a chilling discovery is made when Pappi shows photographs from the party; Damini is completely absent from the photos, and Pappi reveals he saw no one sitting next to Gopal. They realize that Damini was actually Pappi's girlfriend and a housemaid, and the spirit sitting beside Gopal was the Colonel's daughter. As the group panics, Anna reveals the truth: the ghost is actually Khushi.
In a revealing flashback, Khushi explains that she was adopted by Colonel Chauhan and his wife. She had fallen in love with Nikhil Surana (Neil Nitin Mukesh), Jamnadas's nephew. Nikhil was secretly collaborating with Vasu Reddy to seize the orphanage and build an amusement park. When Jamnadas discovered this plot, he threatened to change his will to leave his fortune to Pappi. In a fit of rage, Nikhil murdered Jamnadas. When Khushi confronted him and threatened to go to the police, Nikhil strangled her to death. With Vasu's help, these crimes were staged as accidents. Khushi's spirit had approached Anna for help, and because the five boys had a special connection to her, they were brought to the house to secure justice.
In the climax, Gopal finds the courage to fight Vasu's thugs. While the other boys are initially hesitant, they are eventually convinced to stand their ground. They nearly trick Vasu into a confession, but Nikhil arrives, arrogantly claiming there is no evidence to prove his guilt. A violent struggle ensues, and Khushi's spirit attacks Nikhil, nearly killing him before Anna intervenes to calm her. Ultimately, Vasu convinces Nikhil to confess to his crimes. With the orphanage saved and the truth revealed, Khushi's spirit bids a final, emotional farewell to the boys and Anna before departing for heaven.
