This article contains spoilers from the “Paranormal Activity” series.  

Since the wide release and popularity of “Paranormal Activity” in 2009, the found footage series has become a Halloween staple, with the latest installment being “Paranormal Activity 4.” The series has evolved from a simple ghost story to a complex conspiracy taking up the length of three films to explain, with the fourth film’s trailer boasting, “It has all led to this.”

Katie (Katie Featherson) and Micah (Micah Sloat) are the first to decide to record their home with a set of cameras to monitor the strange things that have been going on since the original “Paranormal Activity,” set in October 2006.  It becomes progressively clearer that there is an entity in the home which eventually possesses Katie, making her kill Micah, with the film’s epilogue saying that her whereabouts were unknown.

Also set in 2006, but before the events of the first film, “Paranormal Activity 2” is a prequel, focusing on Katie’s sister Kristi (Sprague Grayden) and her family. As in the first one, there’s an entity in the family’s home, but this time there is a teenage daughter and newborn baby, Hunter.

When the family starts to figure out that something is wrong and Kristi becomes possessed, they realize that they have to send the evil spirit to someone else: Katie. This leads into Katie and Micah’s interaction with the ghost, with the film jumping forward in time to Katie breaking into Kristi’s house, killing the family and kidnapping Hunter.

Text at the end of the film explained that the teenage daughter Ali wasn’t in their home when Katie broke in, and that Katie and the kidnapped Hunter’s whereabouts remained unknown.

“Paranormal Activity 3” goes back to 1988, when Katie and Kristie were children and had their first interaction with the evil spirit who returns for them parts 1 and 2.

The newest installment will be the first film to be a direct sequel. The film being released on Oct. 19 will take place in November 2011, five years after the disappearance of Katie and Hunter, according to the trailer’s YouTube description.

The movie is about Alice and her mother, who begin to see strange things occur around the house when their new neighbors Katie and Hunter (now renamed Robby) move in.

The film uses the same found footage style as last time, but with some new gadgets thrown in to keep things interesting. At least some portion of the film is going to be shown via video chat, and things like Kinnect for the Xbox 360 are incorporated in the ghost story as well.

The now-annual franchise has kept things intriguing for three similar films, and from the looks of the trailer, the scare tactics are still there with some new touches, just like in the last two installments. Henry Joost and Ariel Schulman return as directors after taking on “Paranormal Activity 3” and the fake documentary “Catfish,” and the two men have made movies in the franchise work before.

When film series get to the fourth entry it gets hard to imagine how things can keep up. None of the sequels can match the simplicity and subtlety of the first “Paranormal Activity,” but so far they’ve been able to stay true to the story and keeping things interesting.

In an interview with MTV, Joost implied that they were going to go big with the fourth installment. "We're trying to blow the lid off," he said, according to MTV.

"At the same time, the warning is always that you don't want to jump the shark. You don't want to be one of those franchises that just goes too big too soon just because you feel that you need to break new ground," MTV claims Schulman added. "What I think makes these movies really special is that they build very slowly. We're not trying to get ahead of ourselves."