A teen comedy follows a group as it tries to have one last night of summer fun, only to be usurped by the world's worst undercover cop.

Steve Martin and Bonnie Hunt return as heads of the Baker family who, while on vacation, find themselves in competition with a rival family of eight children, headed by Eugene Levy,

Cliff receives an unusual 18th birthday gift from his younger sister — marijuana, alcohol, a subway token and the mission to lose his virginity. This results in Cliff meeting a young street hustler named Butch. At first, as Butch introduces Cliff to gay street life in Toronto, Cliff is excited by his new relationship. But as the two grow closer, he finds that Butch has problems, including drug addiction, that are cause for serious concern.

In a suburban landscape, the lives of several families interlace with loss, despair and personal crisis. Esther Gold has lost focus on all but caring for her comatose son, Paul, and neglects her daughter and husband. Lawyer Jim Train is devoted to his career, not his family. Helen Christianson wants to find a new spark in life, while Annette Jennings tries to rebuild hers.

Adrian Monk was once a rising star with the San Francisco Police Department, legendary for using unconventional means to solve the department's most baffling cases. But after the tragic (and still unsolved) murder of his wife Trudy, he developed an extreme case of obsessive-compulsive disorder. Now working as a private consultant, Monk continues to investigate cases in the most unconventional ways.