After the events of the first film, Lou (Rob Corddry) is now a successful businessman, but his life is still a mess. He has lost touch with his friends, Adam (Adam Scott), Nick (Craig Robinson), and Jacob (Clark Duke). The friends are brought back together when Lou's son, Jacob Jr., is kidnapped by a
mysterious figure. The kidnapper sends a holographic video message to Lou, claiming that he has taken his son because he wants to use the
hot tub time machine to alter the past, and Lou is the only one who can help him.The friends are reunited, and they decide to use the hot tub time machine to find Jacob Jr. However, they soon realize that the machine has changed them in unexpected ways. Adam is now a successful and confident businessman, Nick is a rockstar, and Jacob is a genius inventor. Lou, however, is still struggling with his personal demons.As they journey through different timelines, the friends start to realize that the machine has created a new reality, where their past actions have led to a dystopian future. They soon discover that the kidnapper is a future version of Lou, who has traveled back in time to prevent the catastrophic events that led to the dystopian future.The friends must now navigate through different timelines, trying to correct their past mistakes and prevent the apocalypse. Along the way, they encounter alternate versions of themselves, who are struggling to cope with the consequences of their actions. They also encounter a new character, a woman named April (Cassie Steele), who becomes a key player in their mission.As they journey through time, the friends encounter various obstacles, including a group of robotic assassins, a nuclear meltdown, and a zombie outbreak. They also have to deal with their own personal demons, including Lou's struggle with his son's kidnapping and Adam's growing ego.Throughout the film, the friends are forced to confront the consequences of their actions and the true nature of their friendship. They learn to put aside their differences and work together to save their sons and prevent the apocalypse. In the end, they manage to fix the timeline, but not before experiencing a series of surreal and fantastical events.The film ends with the friends returning to their own time, but not before Jacob Jr. is found safe and sound. The friends are finally able to move on with their lives, but not before Lou reflects on the lessons he has learned about the importance of friendship and the consequences of altering the timeline.