Without Warning is obviously rap music as horror film expressionism. Released on Halloween by buzzing Atlanta trap rappers 21 Savage and Migos’ Offset with super-producer Metro Boomin, the mixtape carries all the signifiers in its lyrics, allusions, and sonic cues: eerie cackling, howling winds, jump-scares, skeletons, goblins, bloody Phantoms, Grim Reapers, Jason, and Nightmare on Elm Street. 21 Savage and Metro Boomin know a thing or two about turning murder to bloodsport, as they showed on their 2016 mixtape Savage Mode, which serves as a gory precedent for Without Warning. Now with Offset—one of the most outstanding rappers of 2017—along for the ride, the trio have produced a punishing mixtape where supernatural frights are replaced by guns and goons. The bad guys win.

In the run-up to Without Warning, Metro Boomin has had several run-ins with the project’s billed co-stars. After Savage Mode, he played full-time producer on Gucci Mane’s Droptopwop and Nav’s Perfect Timing. Both of those mixtapes had standout features from Offset—on “Met Gala” and “Minute,” respectively. Soon after, Metro produced the majority of 21 Savage’s debut, Issa Album, which had its own sleeper hit, “Bank Account.” 21 and Offset crossed paths—albeit with Offset as a part of the Migos Ghidorah—on Mike WiLL Made-It’s “Gucci On My,” and the pair teamed-up with Metro as a threesome for the first time on DJ Khaled’s “Iced Out My Arms.” These collaborations mostly yielded mixed results, but Without Warning maximizes the potential of this unholy trinity.

In some sense, 21 Savage and Offset seemed like an odd couple coming into this. They have decidedly different methods: 21 is hostile and inhuman, rapping with the wooden, lifeless delivery of someone numb to violence; Offset is adrenalized and fun-loving, constantly in motion with tightly-wound, precisely-measured, fiercely-performed meters. But they weirdly complement each other here. They each get solo showings but they work mostly in tandem. Offset helps to fill the gaps in 21’s affectless, foreboding execution, keeping those disinterested murmurs from flatlining. Wherever 21’s performances are lacking, Offset adds a touch of showmanship; wherever Offset’s raps become too dense, 2l presents simplicity, concision, and clarity. On “Darth Vader,” Offset raps, “Runnin’ from the demons, angels in my dream when I’m leanin’/Tec-9 wit’ the beam/Don’t nobody move before the shit start ringing.” 21 makes the ideas much more direct: “My dog lost his life and it changed me/I’m poppin’ Percocets ’cause the pain deep/Peel a hot box then we did a drive-by/Get your kids out the street we finna slide by.” One amplifies the other.

The spooks and scares on Without Warning are so contrived and so exaggerated that they just make for big fun. 21 Savage and Offset aren’t undead stalkers or masked slayers but they might as well be. “Wear a hoodie man, I’m the boogie man,” 21 snarls, like a gleeful serial killer taking great pleasure in his conquest: “Another nigga dead, another family scared/Tryna duck the feds.../Paint the city red...” Offset turns pop-up horror fixations into the cornerstone of his cloaked persona. “Come in the middle of the night, like it’s a nightmare/You open your eyes, not dreamin’, nigga we right there,” he raps on “Nightmare.” They dare to reimagine real-life gangland terrors as torture porn. This is Halloween if Michael Myers was Menace II Society’s O-Dog.

Sound design is key to a release like this, and Metro constantly finds the right balance between ghostly and ghastly, striking a tone dark enough for a shudder yet bracing enough for an adrenaline rush. Even counting the gory shriekers on Savage Mode, Metro’s productions have never been this sinister or blood-splattered, dripping bright reds and cloudy carmines. Songs like “Mad Stalkers” and “Run Up the Racks” trade on the pulse-raising booms of 808 drums and minor-key notes. The flourishes are subtle but impactful: the seamless segue from 21’s “My Choppa Hates Niggas” to Offset’s “Nightmare,” the understated tectonic shift beneath the Offset verse on “Rap Saved Me,” the drum programming on “Still Serving,” which bottoms out every few stanzas. Each drop a death rattle ringing out through a deserted town. A campy fiendishness hangs over proceedings like a fog.

The solo songs are as strong as the duets (Offset gets his chance to explode and go full showman on “Ric Flair Drip,” and 21 gets his chance to mutter threats on “Run Up the Racks”), and the tape never loses sight of what it is: a Halloween treat. It’s short and cohesive, an enjoyable and uncomplicated 33 minutes of sheer exhilaration, filled with stings, itches, and cold chills. In one form or another, the collaboration comes as a surprise to all of us, arriving suddenly and carrying within the electricity and satisfaction of a good scare.