A man representing a research lab called CamSET makes an offer on their house in the hopes of developing the area.

Madison and Nikolai set traps and make improvised weapons in hopes of killing the bald man when he rematerializes.

Nikolai regains consciousness and shoots the bald man in the back with one of the dead police officers' guns.

Larter said that although she liked the mix of genres in the film, what drew her to it was the family dynamic and her character's struggle to protect her children.

He was influenced by David Cronenberg for the reality-based monsters, Steven Spielberg's emphasis on likable characters, and John Carpenter's long takes.

The special effects were practical, a decision that Legrand said aided actors in believably reacting to the threats in the film.

[7] Drew Tinnin of Dread Central rated it 1.5/5 stars and wrote, "The Diabolical just doesn’t do enough with its entire running time and it serves as an example of how the new model of an old horror trope with a new twist is growing tired as well.

"[8] Howard Gorman of Scream magazine rated it 4/5 stars and wrote, "With such an imaginative script this film is destined for infinite revisits as you'll want to pinpoint all the telltale signs and clues you missed out on.

"[9] Gary Goldstein of the Los Angeles Times wrote, "The Diabolical is a tepid horror-thriller that never manages to sell, much less clarify, its potentially ambitious concept.