With their lives going nowhere, old college buddies Adam (John Cusack), Nick (Craig Robinson) and Lou (Rob Corddry) return to their favourite ski resort to relive their hard-partying heydays. Sadly, the place is a dump. But after treating Adam's nephew (Clark Duke) to a boozy night in the hotel hot tub, they wake up in a world with no snowboards, no internet, and no fashion sense. Just an illusion? No, it's 1986. So Relax... and enjoy a retro-styled comedy where the laughs are as rude as the hairstyles.
As knowingly daft as it sounds, this amiable - if potty-mouthed - slice of time-hopping silliness represents a third successful partnership between John Cusack (who also produces) and Grosse Pointe Blank/High Fidelity writer Steve Pink (who here only directs).
Written by the team behind bawdy hit Sex Drive, the does-what-it-says-on-the-tin premise reunites three fortyish losers - recently singled Adam (Cusack), unfulfilled musician Nick (Robinson, of The US Office), and loose cannon Lou (Corddry) - after the latter almost gases himself in his garage.
Needing to recapture their youthful mojo, the trio, plus Adam's live-in nephew Jacob (Duke, Hollywood's nerd du jour after Kick-Ass), head for the ski spot where they had their wildest times.
Depressingly, it's now a ghost town. But once the hot tub has been fixed, the boys take the plunge with a few dozen drinks... and wake up in 1986.
At first, they think it's just a day-glo hangover. But with people smoking indoors, talking on mobile phones the size of housebricks, and Ronald Reagan addressing the nation on TV, the situation becomes clear. They're teenagers again (only we see them as their adult selves).
So how come Jacob is there? A good question, which, like most others posed by this most gonzo of comedies, is addressed and then left cheerfully unanswered.
Jacob's role is to worry about getting them all back to 2010 (though they appear to leave in 2006). The others, meanwhile, must keep history intact and prevent the 'butterfly effect' by repeating everything they did on that fateful weekend.
Thus, while Adam is destined to take a fork in the eye from a dumped girlfriend (Lyndsy Fonseca, also of Kick-Ass), Lou has to take several beatings from the resort's resident jocks, and married Nick must endure the guilt of romping one of his band's groupies.
Inevitably, the butterfly begins to flap as the boys variously strike up new romances, profit from their knowledge of the future, and change the musical landscape.
Tripping along to a cracking soundtrack featuring Eighties faves from the sublime (New Order, Spandau Ballet) to the ridiculous (Motley Crue, Poison), it's a colourful trip down memory lane for anyone who ever pulled on a pair of legwarmers or thought they looked good with a perm.
If you're looking for logic and cohesion, you're in the wrong tub. But, disjointed though the set-pieces are, most jog the funny bone and some are genuine belly-wobblers.
Corddry's obnoxiousness gets a trifle wearing, but Cusack is as reliable as ever, Duke gives good geek, and Robinson makes the most of his biggest screen role to date (Nick's over-emotional phone call to his nine-year-old future wife is a scream).
In support, Chevy Chase adds to the Eighties flavour (though not many laughs) as a mysterious hot tub repairman, and Crispin Glover generates both amusement and suspense as a bellhop doomed to lose an arm.
Given Glover's involvement and the film's otherwise blatant self-awareness, there's one blindingly obvious Eighties reference the script refuses to make. McFly? McFlyyy?