If you’re as steeped in horror film mythos as director Adam Wingard and screenwriter Simon Barrett so obviously are, you know full well that a stranger knocking at your door is never a good thing – but that’s the exact kind of expectation the duo, who’ve previously gifted screamer fans with such fare as “You’re Next” and “A Horrible Way to Die,” play with in their latest outing, the wickedly entertaining “The Guest.”

For their latest feature, the dynamic (and occasionally quite devious) horror duo has taken on some heavier material: “The Guest” centers on a family felled by the death of their beloved solider son/brother in the line of duty, a family desperate for something (or could it be someone?) to make them feel just a little bit better. Caleb Peterson’s death has spiraled outward to upend everyone in his family – his parents’ marriage has gone stale, his father’s job is unsatisfying, his younger sister is acting out with an unsuitable boyfriend, and his baby brother is the target of bullies at school.

When his Army pal David (Dan Stevens, who is nothing short of magnetic in the part) knocks on the Petersons’ door, it seems that the smooth-talking charm machine is there to fix all that – is this the vague vow he made to his close pal Caleb before he died? – even (and especially) if that means mowing down everyone who has gotten in the way of the Peterson family’s happiness. Matriarch Laura (Sheila Kelley) lets him in when he randomly shows up one day, because he’s charming and handsome and he knew her son and he walked all that way from the bus station, and she’s confused and sad. Wingard and Barrett aren’t setting up big emotional stakes, but they are laying out believable ones, and “The Guest” keeps its big, human heart pumping throughout its runtime.

David isn’t who (or what) he seems, but that doesn’t stop the Peterson clan from folding him into their ranks – even reticent members like dad Spencer (Leland Orser) and sister Anna (Maika Monroe) give into his sway, and baby brother Luke (Brendan Meyer) is quickly sold on David’s talents (like beating up bullies in raging bar fights). Wingard and Barrett are adept at navigating the dueling tones that make up most horror outings, effectively mining both terror and humor, gore and guffaws. It’s their primary filmmaking strength and, fortunately enough, it only seems to be getting bigger and better with each subsequent film. Wingard and Barrett know their traditional horror films, though, and “The Guest” oozes eighties cool and the kind of sharp humor that could only come from a deep knowledge of, and deep respect for, the kind of slashers from which “The Guest” creatively cribs. Hell, it even takes place during Halloween.

The film’s sweeping third act reveals – the kinds put into place to talk away everything that’s happened before, a necessary narrative device but the type that dilutes power in a big way – disappoint, not just because Barrett’s script tries to tie everything up into a neat little bow, but because the explanations simply don’t jive with the material. Wingard and Barrett’s tone-heavy and character-driven feature doesn’t benefit much from a high concept “twist” that would feel far more appropriate in a film like “Cabin in the Woods.” The charm of “The Guest” – and, yes, this is a slasher film that has charm to spare – isn’t rooted in nifty simplifications and narrative shocks, and such movements bog down an otherwise strong film’s final act.

Its keen visual sense of humor (a sight gag involving Stevens emerging from a steamy bathroom is an instant classic) set the film a cut above its brethren, a truly entertaining and dizzyingly wild horror film with its own point of view and special delights. Despite all its vintage touches (all those eighties-esque jams) and traditional tropes (there’s even a Halloween dance to attend), the film is weirdly timeless and should entertain horror fans for years to come (and, yes, it will likely serve as a funny “Hey, remember when Dan Stevens played that total madman in that horror film?” once the “Downton Abbey” actor inevitably becomes a giant star). It’s got guts.

SCORE: 7.2 / 10