Following a hurtful divorce, Theresa Osborne (Robin Wright Penn) fills her life with caring for her son, Jason, and working as a researcher at the Chicago Tribune. Since the death of his wife Catherine, Garret has lead a solitary existence, except for his relationship with his father, Dodge (Paul Newman), who attempts to wrest his son away from his grief for Catherine.

On a solitary holiday while Jason visits his father, Theresa is walking along a deserted stretch of coastline when she discovers a bottle containing a moving, passionate letter, signed simply, "G." The letter's poetry and heartache reach out to Theresa, prompting her to begin a search for the author that eventually leads her to the Outer Banks of North Carolina, to a sailboat builder named Garret Blake (Kevin Costner).

Adam was born in a steel bunker buried in his parent's backyard, an unforeseen product of the "duck-and-cover" era taken to its extreme. The son of brilliant-but-paranoid scientist Calvin Webber (Christopher Walken) and picture-perfect suburban wife Helen (Sissy Spacek), Adam's bizarre upbringing was the result of a major tactical mistake. In the midst of the fearsome Cuban Missile Crisis, the Webbers witnessed a blast they thought must be the Big One, but was actually a plane crashing into their yard. So it was that they ensconced themselves in their elaborately engineered bomb shelter to wait out the half-life of radioactive contamination. For 35 years, Adam was raised on Jackie Gleason re-runs, Perry Como records and dreams about life on the surface. While his father taught him about science, baseball and avoiding Communists, his mother taught him about dancing, manners and charming girls. Meanwhile, he waited and waited for a chance to see the sky.

Eve, on the other hand, grew up in a rapidly changing Los Angeles and emerged as a woman suspicious of intentions, savagely smart about survival and pretty darned uncertain about the possibilities of love. Her life has been a series of dead-end jobs, shallow boyfriends and dashed hopes.

Now, for the first time, Adam is about to leave the safety of the underground for the overwhelming complexity of the '90s - and Eve is about to get a whole new perspective on life. When the time-triggered locks on the Webber's shelter at last open, Adam is sent out to replenish supplies and find a nice, non-mutant girl from Pasadena in order to repopulate the world with upstanding citizens.

Adam's hapless search in the brave new world of homeless people, adult book stores and all-night supermarkets leads him smack into Eve. At first, she just can't believe this guy who says "Ma'am," thinks seersucker jackets are stylish, and has never seen color television, is for real. But the more Eve watches Adam approach the world with wide eyes, comic miscomprehension, joyous delight and a deliciously sweet innocence, the more she begins to find herself falling . . . in love?

But the question still remains: can these two find happiness in the real world, or will their sparks send Adam back underground?

Ambitious television reporter Tim O'Hara (Jeff Daniels) stumbles upon a real-life Martian (Christopher Lloyd) whose space ship has crash-landed on Earth. Believing this is the story of the millennium and his chance for a Pulitzer Prize, Tim makes plans to expose the Martian who, posing as Tim's Uncle Martin, takes human form with plans of his own.

Obviously, Uncle Martin doesn't want to be identified. In fact, all of Tim's efforts to divulge the truth are systematically thwarted by the resourceful alien who ultimately recruits Tim to help him repair his ship for a return to Mars. They eventually become pals and join together to overcome the many hilarious obstacles that confront them along the way.