Dean Devlin has, over the last two decades, worked with some of Hollywood's brightest talents on several of history's biggest studio blockbusters. His new movie, Bad Samaritan, couldn't be further from a studio film — he financed it entirely on his own — but the performance by its protagonist rivals any that Devlin has witnessed on his sets.

In fact, as both a filmmaker and lifelong Doctor Who fanatic, Devlin found watching former Time Lord David Tennant's on-set transform from genial British chap into remorseless serial killer to be absolutely unnerving.

"Some actors have to stay in character all the time, but David's the guy who literally can just hit the switch on and off. So before the take, he's literally the sweetest man you've ever met, helping people carry their props onto the set, pouring coffee for you, and chit-chatting, being very sweet," Devlin says in a new episode of The Fandom Files. "And the minute I would say ‘Action,' you could literally see the muscles in his face moving and his eyes clouding over and getting dark and suddenly it was really uncomfortable to be on set. I'd see crew members starting to shift around and feeling uncomfortable."

Tennant's cold, calculating, creepy murderer is on a mission to eliminate the unluckiest valet parker in the world after the kid tries to rob his home in a small-time crime scheme gone awry. Instead of making off with a few valuables and maybe some cash, Sean (played by Robbie Sheehan) finds a bound-up woman in brief respite from being tortured by Tennant's clearly psychotic Cale Erendreich, who gave Sean bad vibes from the moment he tossed him his car keys. Sean decides to split, but the image of the girl weighs heavily on him — as it should — and he winds up in a cat-and-mouse game with an absolute madman.

The movie was shot on a relatively short schedule in Portland and lacks any of the aliens or time travel present in most of Devlin's best-known works, including Independence Day and The Librarians, among many others. Tennant has also made a career in science fiction, but needed no astral assistance in this film.

"He's brilliant in Jessica Jones, and I think it's a brilliant show, but relies on a supernatural power in it," Devlin says. "What makes David so terrifying in this is that he's created a completely, 100 percent grounded psychopath. This guy could live down the hall from you. This guy could live across the street from you — and probably does. He did an enormous amount of research on people who have no ability to feel guilt or have empathy for other people. He constructed a truly terrifying villain."

Video of Exclusive Sneak Peek: Bad Samaritan Starring David Tennant | SYFY WIRE

And yet despite the searingly villainous turn by a well-known actor, Devlin knows what Bad Samaritan is up against. Avengers: Infinity War just had a record-setting opening weekend, taking in over $250 million, and it should rake it in this coming weekend, when Bad Samaritan is set to hit theaters. And so Devlin is barnstorming with the movie, taking a grassroots marketing approach that befits a film he made on his company's own dime. They're barnstorming across the country, holding Q&As at screenings, trying to get the word out organically. They may have an ally in the semi-controversial moviegoing ticket app MoviePass, which allows (some) viewers to attend movies every single day for one yearly fee.

"I think it's a huge help, because what it could do is bring back the desire to go to movies," Devlin said, explaining that it could foster a new cinema culture. "When I was growing up, a group would go to the movie theater and look and see what's playing. Nobody does that now. People know what movie they want to go see, and they go see it. If it could get people back into the habit of going to movies and understanding why it's a unique and special experience, then I think it's going to be really worth it. They're just going to have to balance the privacy issues of their users versus their ability to offer marketing."

As it stands, big event movies, which are now cultural must-sees, suck up most people's theater-going budgets. With unlimited (or at least less limited) moviegoing opportunities, it's more likely that they'll discover movies like Bad Samaritan… and then be terrified of their neighbors.

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