As a franchise, “Insidious” scares by taking the viewer into the astral plane. This realm holds the ability to unleash unspeakable horrors, especially if the characters venture into the shadowy zone known as “The Further,” which is essentially purgatory for all the naughty spirits that you don’t ever want to meet. Seriously, there’s no place for Casper the Friendly Ghost here, because this is the hangout spot for the likes of the Lipstick-Face Demon (Joseph Bishara) and the Bride in Black (Philip Friedman and Tom Fitzpatrick).

The same team behind “Saw” brought “Insidious” to life in 2010, with Leigh Whannell penning the script and James Wan directing the movie. Since then, the story has expanded further into various prequels and sequels. There seems to be no end in sight for this franchise either, as the “Insidious” timeline has so much to it that we had to step in to help explain it. It more than rivals the lore of the similar horror franchise “The Conjuring.”

In terms of ranking the “Insidious” movies, it’s important to look at the franchise as a whole and how the various stories tie into each other. Resultantly, the below isn’t based on Rotten Tomatoes rankings, but instead the common sense applied by franchise fans.

Set before the events of “Insidious,” 2018’s “Insidious: The Last Key,” written by Leigh Whannell and directed by Adam Robitel, follows paranormal investigator Elise Rainier (Lin Shaye), as she receives a call to investigate paranormal activity at her childhood home. Not only is she forced to face the immediate threat in front of her, but she also needs to unlock secrets from her own tragic past.

From a thematic perspective, “Insidious: The Last Key” is about confronting figurative and literal demons, as well as childhood trauma, but it stumbles into every single cliche and pitfall of the genre. It isn’t unwatchable by any means, but compared to the rest of the entries in the series, this hardly feels like it belongs in the same league. Also, why does it feel like this movie is shoehorned into the “Insidious” timeline? That may be because it is. As we explain in our guide to understanding the ending of “The Last Key,” it takes a last minute dream sequence to tie this to the start of the original film.

On the bright side, Shaye proves she doesn’t know how to give a bad performance if her life depended on it, making everyone appreciate how important Elise is as a character to the series. In addition, Elise’s chemistry with her fellow paranormal investigators, Specs (Leigh Whannell) and Tucker (Angus Sampson), stays off the charts. It is always a welcome experience to see these three interacting on screen.

James Wan and Leigh Whannell return as the braintrust behind 2013’s “Insidious: Chapter 2.” The sequel picks up after the shocking events of the original movie, where Josh Lambert (Patrick Wilson) is possessed by the ghost from his childhood and snaps Elise Rainier’s neck. Viewers learn more about Josh’s past as a child and his own experiences with the astral plane, as well as how, as an adult, his family fights to bring him back before the evil spirit succeeds in killing him.

As far as sequels go, “Insidious: Chapter 2” follows the right path by answering questions that audiences might have had after watching the first film. However, it also repeats a lot of the same story beats. Perhaps it was an unreasonable expectation to begin with, but the sequel doesn’t possess the titillating thrill and chilling charm that “Insidious” brought to the party.

In terms of positives, Wilson clearly has the time of his life playing a possessed Josh. He seems to channel a bit of George Lutz from “The Amityville Horror” into his performance, as the evil takes him over and his family become targets. Rose Byrne deserves credit for her turn as Renai Lambert too — in a short period of time, this poor woman nearly loses her child and husband to supernatural forces, but she still keeps it together under pressure.

The first time the franchise breaks off from the Lambert family occurs in 2015’s “Insidious: Chapter 3.” Written and directed by Leigh Whannell, this prequel film centers around Elise Rainier assisting the Brenner family with their paranormal woes.

What happens here is that teenager Quinn Brenner (Stefanie Scott) asks Elise to help her make contact with the spirit of her mother who died a year earlier. Elise senses an evil presence and warns Quinn to not mess with the world of the dead, or bad things will happen. Naturally, that’s exactly what occurs. A brutal accident also leaves Quinn with two broken legs, leaving her bed-bound at home. That makes it showtime for the ghouls to come and play, since Quinn has no way to run or hide.

Thematically, “Insidious: Chapter 3” doesn’t diverge from the ghosts of the past concept from the previous films, and you will see familiar things that happen in every “Insidious” movie. However, the spine-chilling scenes and well-timed jump scares more than make up for the lack of originality. The fact that Quinn is injured and can’t go anywhere adds to the tension and terror, since she’s a sitting duck for the spirits to strike. Plus, the main antagonistic spirit of the film, the Man Who Can’t Breathe (Michael Reid MacKay), leaves quite the impression on the viewer.

After a detour into other stories, the franchise returns to Josh Lambert (Wilson) and his son Dalton (Ty Simpkins), in 2023’s “Insidious: The Red Door.” Directed by Patrick Wilson from a script by Scott Teems, the film addresses the question that every fan had after “Insidious: Chapter 2”: What happens to Josh and Dalton after they were possessed and had their memories wiped?

This film provides answers. Josh is now divorced from Renai, while his relationship with Dalton, who is now at college, isn’t great. Both of them feel burdened, but they’re unsure by what — until eventually Dalton finds out the truth about their past. As Dalton ventures back into “The Further,” both he and Josh uncover more about their family’s history. Josh and Dalton will have to work together and sort out their issues to make it out alive.

At its core, the story of Josh and Dalton is about passing down generational trauma and dealing with mental illness. They grapple with ghosts of the past, but in order for the cycle to stop, they need to forgive themselves and each other for what already happened. In terms of all the entries in this series, “Insidious: The Red Door” hits our emotions the hardest, showcasing how it is never too late to repair relationships. In addition to this, the end credits feature an excellent cover of the Shakespears Sister hit song “Stay,” performed by the band Ghost with guest vocals by Patrick Wilson. It’s simply the perfect song for this movie.

Despite all efforts, nothing tops the original “Insidious.” Produced for a paltry budget of $1.5 million, director James Wan and writer Leigh Whannell made magic by focusing on practical scares and a compelling story about family. It’s all about the atmosphere here, as the film leers and sneers with an ominous threat. Special credit goes to composer Joseph Bishara, who also appears as the Lipstick-Face Demon, for an outstandingly creepy score.

In this story, Josh and Renai Lambert do everything in their power to look after and help Dalton, who falls into a coma under bizarre circumstances. While the Lamberts move out because they believe their home is haunted, they soon discover that Dalton astral traveled to a plane that he now can’t escape from. It’s something that Josh could do when he was young, and he will need to do again to save his son.

“Insidious” concludes on a disturbing and unexpected ending. After everything the characters go through, Wan and Whannell have one more surprise for you that can still send shivers down the spine years later. “Insidious” is one scary movie — if not the most terrifying horror film of all time.