Finding a ghost named Ernest haunting their new home turns Kevin's family into overnight social media sensations. But when Kevin and Ernest investigate the mystery of Ernest's past, they become a target of the CIA.

Five years after the events of the first film, Lou Dorchen and Nick Webber have become Wealth and Celebrity, with Lou becoming a multi-billionaire and Nick being a successful music singer. At Lou's celebratory party, Lou is shot in the groin. Jacob (Lou's son) and Nick drag him to the hot tub time machine and activate it to travel back in time to find and stop the killer. When they awaken they find themselves ten years in the future, where Jacob is in charge of Lou's mansion. After determining that they are in an alternate timeline where Lou's killer is from this future, they go to their friend Adam Yates's home, only to meet his son Adam Yates Stedmeyer (Adam Jr.) who is engaged to a girl named Jill.