If there's one thing Leigh Whannell learned from William Friedkin about directing horror movies, it's this: you have to scare your actors for real.

Flash back to early 2014. Whannell has signed on to direct "Insidious: Chapter 3," a prequel to 2010's "Insidious" and 2013's "Insidious: Chapter 2," both helmed by his longtime creative partner James Wan. It's his directorial debut. He's anxious and looking for guidance, so he tweets at Friedkin asking for his advice.

Friedkin responds within just a few minutes. Friedkin invites him out to lunch.

"It was surreal," says Whannell, chatting with reporters on the "Insidious: Chapter 3" set in Lake View Terrace, CA alongside cast members Dermot Mulroney, Stefanie Scott, Lin Shaye, Angus Sampson and producer James Blum. "He comes and he sits down.  I'd never met the guy.  And he barely said hello.  He was just like, 'First of all, you've got to scare your actors for real.  Every time somebody jumps in 'The Exorcist,' it's because I was just off camera firing a gun. Do you think I could've got [that] priest to jump like that when the phone rang?  No.  I shot a gun. ...That's what you must do.'"

Whannell's mission was clear.

Stefanie Scott in Insidious Chapter 3
Stefanie Scott as Quinn Brenner

"I mentioned it to [first assistant director Dan Lazarovits]. I was like, 'I just want you to know...I'm going to have to have some guns.'  And he was like, 'No, you won't be doing that.'  And I'm like, 'Of course, I won't.  That would be stupid.'"

His "consolation prize"? An air horn. Which was used...well, at least once.

"I’ve definitely tried to create an atmosphere and get everyone into it," says Whannell.

It's a strategy that certainly wasn't lost on his actors.

"One time I came in, and it literally happened -- what Leigh was hoping all along -- is that I'm just doing a scene about breakfast or getting the kids ready, and then behind me there's a guy sitting there that I'd never seen him, and he's in the full regalia of this demon, ready to go on to do his part," says Mulroney, citing just one example of the spooky vibe Whannell created on set. "But he's lurking in the corner, and it's dark, and it's like really, really creepy."

"[Leigh] just scares the crap out of me every day," chimes in Scott, best known for her role on the popular Disney Channel sitcom "A.N.T. Farm."

Echoes Shaye: "It's very gloomy."

Dermot Mulroney in Insidious Chapter 3
Dermot Mulroney as Sean Brenner

Speaking of Shaye, the series' third installment will function as something of an origin story for the actress's paranormal researcher Elise Rainier and her two sidekicks Specs (Whannell) and Tucker (Sampson), characters featured prominently in the first two films. The prequel approach allowed Whannell to bring Shaye's character, who died at the end of the first film, out of the Further ("You don't want morbid ghost Lin Shaye, you want full on, turbocharged Lin Shaye," he says) and back into the world of the living whilst keeping a "connective tissue" to the first two movies. He also wanted to avoid the feeling of deja vu that may have come from having the Lamberts (played by Rose Byrne and Patrick Wilson) return for yet another round of supernatural mayhem.

"They'd been through so much with all this stuff that had gone on, and I think it would have been weird for the trailer to be, like, 'They’re back!  And they're being haunted!  Again!'" says Whannell, who goes on to add: "Haunted house movies are always built on this feeling of what's going on.  You know, if you put Rose Byrne and Patrick Wilson in this movie and the teacup moves, they’re like, 'Oh, shit, it's a ghost again.'  They're so knowledgeable by now that they could be experts themselves."

In place of the Lamberts, "Chapter 3" introduces Sean and Quinn Brenner (Mulroney and Scott), a father and daughter who are tormented by a malevolent supernatural entity following the death of wife and mother Lillith (Ele Keats) from cancer. The loss experienced by the characters is quite literally given physical form with a demon named in the credits as The Man Who Can't Breathe -- described by Whannell as "the living embodiment of cancer." The spook in question is played by Michael Reid MacKay, the wiry actor who was also responsible for arguably the most terrifying moment in David Fincher's "Seven."

"I actually said to [special effects makeup designers] Fracture Effects, I was like, 'You know the guy Sloth from 'Seven,' that he tied to the bed and kept him there for a year?'  And so that's who we got, that guy, Michael MacKay, the actual guy who was tied to the bed.  You know, he's a couple of years older now, but he's that guy.  And he just is so great in the role."

A former contributor to sites including MTV's The Backlot and Bloody-Disgusting, Chris Eggertsen worked in film development before indulging his love of pop culture writing full time. He specializes in horror, the intersection of social issues and entertainment and Howard Stern. He's on Twitter @HitFixChris.