Flamboyant mobster Vinnie (Steve Martin) is relocated by the Witness Protection Program from New York City to suburban California until it is time for him to testify against his former associates. But he quickly bores of life in middle-class America and starts up his own little racket. These shenanigans cause Vinnie to run afoul of the local authorities, which makes life difficult for the straitlaced FBI agent (Rick Moranis) assigned to protect him. Soon the agent is struggling to keep Vinnie out of the clutches of a tough-as-nails assistant D.A. (Joan Cusack) who wants to see him behind bars.