Insidious is a 2010 supernatural horror film directed and co-edited by James Wan, written by Leigh Whannell, and starring Patrick Wilson, Rose Byrne, and Barbara Hershey.

The story centers on a married couple whose boy inexplicably enters a comatose state and becomes a vessel for a variety of demonic entities in an astral plane.

Insidious had its world premiere on September 14, 2010, at the 2010 Toronto International Film Festival (TIFF) and received a wide theatrical release on April 1, 2011, by FilmDistrict.

Married couple Josh and Renai Lambert have recently moved in to a new home with their sons, Dalton and Foster, and their infant daughter Kali.

Elise explains that Dalton is not in a coma; he was born with the ability to astral project his consciousness and had been unknowingly doing so in his sleep, believing he was simply dreaming.

[9] Principal photography for Insidious was completed over the course of three weeks in 2010, from late April to mid-May at the historic Herald Examiner Building in downtown Los Angeles.

[10] Performed with a quartet and a piano, a bulk of the score was improvised and structured in the editing process, although some recording sessions began prior to filming.

[12] On describing the approach of the film's soundtrack, director James Wan explained, "We wanted a lot of the scare sequences to play really silent.

But, what I like to do with the soundtrack is set you on edge with a really loud, sort of like, atonal scratchy violin score, mixing with some really weird piano bangs and take that away and all of a sudden, you're like, 'What just happened there?

[23] Roger Ebert gave the film two-and-a-half stars out of four and wrote, "It depends on characters, atmosphere, sneaky happenings and mounting dread.

Mike Hale of The New York Times wrote that "the strongest analogue for the second half of Insidious is one that the filmmakers probably weren't trying for: it feels like a less poetic version of an M. Night Shyamalan fairy tale.

"[26] Ethan Gilsdorf of The Boston Globe wrote that "[t]he film begins with promise" but "[t]he crazy train of Insidious runs fully off the rails when the filmmakers go logical and some of the strange gets explained away as a double shot of demonic possession and astral projection.

"[28] Michael Phillips of the Chicago Tribune wrote: "director James Wan and screenwriter Leigh Whannell admire all sorts of fright, from the blatant to the insidiously subtle.

"[29] Peter Travers of Rolling Stone commented: "Here's a better-than-average spook house movie, mostly because Insidious decides it can daunt an audience without spraying it with blood.

A third installment, Insidious: Chapter 3, with Leigh Whannell serving as director and writer, was released on June 5, 2015, to a high box office gross and a mixed critical response.

[33] A fourth installment, with Adam Robitel as director and Whannell as writer of the film,[34] Insidious: The Last Key was released on January 5, 2018, and received mixed reviews.