There’s no running from conspiracy theories. In some ways, our species is defined by our habit of attempting to explain strange or incomprehensible incidents with interlocking narratives of our own design. In fact, our desire to connect the dots of the universe is likely responsible for cultural phenomena like science, philosophy and even spirituality, and it’s only become more prevalent with the rise of the internet. Of course, there’s a darker side to conspiratorial thinking, as it can often lead vulnerable people down a dark rabbit-hole of paranoia and isolation.

From Chris Carter’s The X-Files to Darren Aronofsky’s Pi, there are actually quite a few examples of popular media that explore the world of conspiracy theories, though only a few of these are willing to examine how psychologically damaging this kind of obsession can be. One of the absolute best of these conspiratorial yarns happens to be the 2006 psychological horror film Bug, an underappreciated descent into madness directed by the living legend behind The Exorcist, William Friedkin.

Based on the homonymous stage production by award-winning playwright Tracy Letts (who would later partner with Friedkin on another underseen gem with 2011’s Killer Joe), Bug tells the story of Agnes White (Ashley Judd), a waitress with a troubled past who befriends the ex-military drifter Peter Evans (Michael Shannon). The two quickly become close, bonding over their mutual loneliness, but Peter soon reveals that he believes he’s being pursued by the government and insists that Agnes’ motel room is infested with sinister little insects. Agnes is initially skeptic of Peter’s outlandish claims, but soon joins his crusade against the parasitic bugs in a tragic case of folie à deux that escalates into tragedy.

While the first half of this slow-burn thriller is mostly dedicated to setting up Agnes and Peter’s budding relationship, containing more than a few genuinely touching moments as these two strangers slowly open up about their emotional vulnerabilities, it eventually becomes clear that things will be taking a turn for the horrific. These microscopic invaders might not seem all that terrifying at first, especially when you don’t even know if they’re real, but the paranoid horrors suggested by Bug are much larger and more tangible than any physical monster.

It’s just a little love bite, right?

Friedkin was extremely dissatisfied with the movie’s original marketing campaign, which sold the feature as a more traditional horror flick instead of a self-contained dramatic thriller. Similar to The Exorcist, which the director has always claimed to be an uplifting tale about being able to love a stranger so much that you’d be willing to die for them, Friedkin insists that Bug is actually a genuine love story surrounded by horrific circumstances. While he has a point about the marketing, as the misleading trailers resulted in general audiences absolutely despising the film on release, I don’t necessarily agree with the director’s assessment that this isn’t a horror story. It may focus on the characters and takes a while to get going, but Bug is still one hell of an effective scary movie.

With sub-dermal parasites and cringe-inducing moments of horrific self-mutilation, the film employs quite a few elements of body-horror as it explores the terrifying extremes of madness and paranoia. With all that nasty talk about tiny egg sacs and microscopic implants, I wouldn’t blame you for wanting to take a shower once the credits roll, and don’t even get me started on that tooth extraction scene. Even so, the physical aspect of the characters’ suffering is only half the story, as the psychological damage is much more terrifying.

From implied government surveillance to suspicious helicopters flying over the motel, Bug‘s greatest achievement is in never actually confirming if Peter’s paranoia is truly baseless. References to horrific real-world conspiracies like MK-Ultra and other military experiments ground the story in reality, planting a dangerous seed of doubt that’s much scarier than any real infection. These believable elements are combined with absurd fantasies in order to put viewers in the same conspiratorial mindset as the ill-fated protagonists, leading to more than a couple of moments where you really want them to be right.

Even though Peter initially means well by exposing these terrible “secrets” to Agnes, his refusal to listen to reason eventually results in him dragging her down with him like a manic drowning victim. Even then, Agnes isn’t completely blameless, encouraging Peter’s toxic behavior when she realizes that sharing this hidden knowledge brings them closer together, and pushing people away when they attempt to help.

Love hurts.

Of course, the conspiracies are only this convincing because of the Oscar-worthy lead performances by Shannon and Judd. Shannon is actually reprising his role from Letts’ original stage show, and this is without a doubt one of the best acts of his career. Despite Peter’s manic rambling and paranoid delusions, there’s never any doubt that he’s a decent person underneath all that trauma, and you can’t help but sympathize with this hapless loner and his predicament. Judd is phenomenal as well, with Agnes smoothly and believably transitioning from helpless lover running from her past to the delirious “super mother bug” in the span of a couple of hours.

With awe-inspiring performances and nuanced direction by a true master of the craft, it’s hard not to feel a rush of conflicting emotions when Bug reaches its dreadful climax, bringing this genuinely loving yet toxic relationship to a fiery end. The deliberate pacing and subtle plot progression might not be for everyone, but there’s no denying that there’s some authentic passion behind this weird little film, and I wish more horror fans would bring it up when discussing Friedkin. Hell, the movie never even got a Blu-ray release in North America, which cements it as a bona fide overlooked gem in my book.

At its core, Bug truly is a heart-wrenching love story (and a damn good one, at that), but it’s also a chilling exploration of how conspiratorial narratives can lead lonely and vulnerable people to hurt themselves and others as they search for validation. In today’s post-truth environment, where there’s barely a difference between so-called “fake news” and legitimate journalism, I’d say that the idea that paranoia is contagious is scarier than ever. That’s why I’d recommend Bug to any horror fan willing to jump into a mind-bending rabbit hole. Just be sure to stock up on tin foil and insecticide before you dive in.