“It might all seem normal and routine,” declares Davey Armstrong (Graham Verchere), the hero of Summer of 84, “but the suburbs are where the craziest shit happens.” That was already old news by the year this nostalgic thriller is set, of course, but the movie — directed by the Montreal collective of Francois Simard, Anouk Whissell and Yoann-Karl Whissell — deserves credit for playing it out in a way that echoes its thesis.

Summer of 84 might seem normal and routine at first, another It-ride on the Stranger Things–cycle, back to the childhood of white boys entranced with George Lucas, Steven Spielberg and John Carpenter. But by the end, the craziest shit has happened, persuasively, with both memorable style and some emotional power. At first, it seems most concerned with showcasing vintage toy collections and putting ribald pop-culture talk into the mouths of kids — weep for the line about “buttfucking Wookiees.” But once Summer of 84 kicks in, it kicks hard, and in its darkest moments, I was hoping the filmmakers had sprung on us a dream-sequence fakeout, perhaps in honor of Brian De Palma.

That ending slices so sharply thanks to a protracted, un-spectacular setup. Like a 15-year-old’s actual ’80s summer, the film has its languors. The plot concerns skinny dreamer Davey, a fanatic for Bigfoot creatures and aliens of supermarket tabloids, suddenly convinced that the loner cop (Rich Sommer) who lives across the street must be a serial killer responsible for a spate of missing kids. Davey enlists his three noisome, horndog buddies to track the dude, dig up his garden, map out his jog and the usual Rear Window–style stealth missions.

In the early going, we’re subjected to much historically accurate chatter about the boys’ masturbation habits, more than any audience could truly need, but I appreciate the filmmakers’ honesty. The boys become more endearing as the film wears on, but like real boys, their greatest talent is to find a way to spin anything anyone ever says into filthiness. A throbbing and effective synth score works overtime to sell the film’s first half as suspenseful, though it’s not. (It also clangs annoyingly, overbearingly whenever the characters get startled.) Also initially unpromising: Davey peeps through his bedroom window at a high school beauty (Tiera Skovbye) next door who’s — ick — kind of into it.

If you’re patient, though, and not put off by the familiarity of this material, Summer of 84 gains in interest and urgency as it goes. Sommer (Mad Men’s Harry Crane) makes a first-rate is-he-or-isn’t-he creep, his unctuousness indistinguishable from wickedness. The last 40 minutes zip tensely along, including the priceless scene of Davey’s father marching the boys right over to that cop’s house and making them each apologize to his face for having gone through his trash and suspecting him of murder. It’s hilarious, uncomfortable, original and the start of something new in what had until now been a saltily comic retread: It’s scary.