After bowler Roy Munson swindles the wrong crowd and is left with a hook for a hand, he settles into impoverished obscurity. That is, until he uncovers the next big thing: an Amish kid named Ishmael. So, the corrupt and the hopelessly naive hit the circuit intent on settling an old score with Big Ern.
It's Christmas time and the Griswolds are preparing for a family seasonal celebration, but things never run smoothly for Clark, his wife Ellen and their two kids. Clark's continual bad luck is worsened by his obnoxious family guests, but he manages to keep going knowing that his Christmas bonus is due soon.
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.