Seeking to bring some youthful optimism back to their failed, miserable lives, three middle-aged guys -- Adam (John Cusack), Nick (Craig Robinson), and Lou (Rob Corddry) -- go to a mountain resort where they spent some of their wildest days (reluctantly dragging along Adam's nephew, Jacob, played by newcomer Clark Duke). A drunken accident in the titular hot tub sends them swirling back to 1986, where each of them decides to risk changing the future (and possibly erasing Jacob from existence) by doing things just a little differently.