Decades ago, Adam (JOHN CUSACK), Lou (ROB CORDDRY) and Nick (CRAIG ROBINSON) were best friends who always hung out and partied together. Now, however, they've grown apart and are a generally unhappy lot. Nick runs a dog shop where he must retrieve things canines have eaten, Adam's girlfriend has left him and taken half or more of their possessions, and Lou is once again suicidal.
His latest attempt reunites the three friends and they decide, with Adam's 20-year-old nephew Jacob (CLARK DUKE) in tow, to return to a ski resort, one of their favorite and wild vacation spots from the past. Things don't start off on a promising note, however, as the town isn't as lively as they remember and the lodge's bitter, one-armed bellhop, Phil (CRISPIN GLOVER), doesn't particularly make them feel welcome. But the hot tub appears to be working, so all four men jump in, drink heavily, and accidentally short out the tub's electronics.
Unbeknownst to them, that's sent the four guys through some sort of time portal back to 1986 and one of their previous vacations there. While Jacob appears as himself, and the three friends still see each other in their current, middle-aged state, everyone else sees them as they appeared as teens back in the mid eighties.
All of which means Lou is going to have a bad run-in with ski bully Blaine (SEBASTIAN STAN), while Adam is still going to be dating Jennie (LYNDSY FONSECA) but find himself attracted to rock 'n roll reporter April (LIZZY CAPLAN). Nick will be in a groupie-attracting band and thus worry that he's going to cheat on his 21st century wife, Courtney (KELLEE STEWART), and Jacob is going to realize that his mom, Kelly (COLLETTE WOLFE), was a promiscuous partier.
They understand that they need to make sure everything plays out exactly as it did back then to avoid changing the future. Yet, they're tempted by reliving their wild youth along with thoughts of possibly making changes they think could improve their lot in life. Accordingly, as a mystical maintenance repairman (CHEVY CHASE) occasionally shows up reporting on a pending deadline to return to the future, the men must decide what they want to do.