When his boss is killed, Detroit cop Axel Foley finds evidence that the murderer had ties to a California amusement park called Wonder World. Returning to sunny Beverly Hills once more, Foley reunites with Detective Billy Rosewood to solve the case. Along with Billy's new partner, Detective Jon Flint, they discover that Wonder World is being used as a front for a massive counterfeiting ring.
Mason Storm, a 'go it alone' cop, is gunned down at home. The intruders kill his wife, and think they've killed both Mason and his son too. Mason is secretly taken to a hospital where he spends several years in a coma. His son meanwhile is growing up thinking his father is dead. When Mason wakes up, everyone is in danger - himself, his son, his best friend, his nurse - but most of all those who arranged for his death
On July 2, a giant alien mothership enters orbit around Earth and deploys several dozen saucer-shaped 'destroyer' spacecraft that quickly lay waste to major cities around the planet. On July 3, the United States conducts a coordinated counterattack that fails. On July 4, a plan is devised to gain access to the interior of the alien mothership in space, in order to plant a nuclear missile.