The film begins with Josh (played by Patrick Wilson) and Renai Lambert (played by Rose Byrne) moving into a new home with their three children, Dalton (played by Ty Simpkins), Foster (played by Andrew Astor), and baby Cali. Shortly after moving in, strange and unexplainable events begin to occur, including Dalton’s sudden and unexplained coma.
In the climax, Renai becomes increasingly disturbed by paranormal activity in the house, including strange voices and apparitions. Josh, a school teacher, dismisses her concerns at first but begins to experience strange occurrences himself. Renai contacts a paranormal investigator named Elise Rainier (played by Lin Shaye) for help.
As the plot unfolds, Elise and her team investigate the Lambert’s home and discover that Dalton is not in a coma but has unknowingly traveled to a realm called “The Further,” a place inhabited by malevolent spirits. Elise explains that Dalton’s ability to astral project while sleeping has made him vulnerable to possession by these spirits.
In the resolution, Elise helps Josh learn to astral project so that he can enter The Further and rescue Dalton. Josh successfully locates Dalton but discovers that an evil entity known as the “Red-Faced Demon” is trying to possess him. With Elise’s guidance, Josh is able to save Dalton and bring him back to the real world.
The film concludes with the Lambert family moving into a new home, hoping to leave the horrors of their past behind them. However, in a chilling final scene, it is revealed that Josh himself has been possessed by the Red-Faced Demon, setting the stage for the film’s sequels.
“Insidious” is praised for its effective use of suspense, atmosphere, and jump scares, as well as its original take on the haunted house genre. It explores themes of family, trauma, and the supernatural, making it a standout in the horror genre.