The star plays an image consultant named Russell Duritz whose clients are scumbags and whose life consists mainly of barking into cell phones, snapping at his assistant (played by Lily Tomlin, who is nobody's doormat) and avoiding a meaningful relationship with a morally centered woman named Amy (Emily Mortimer). Into his rich, empty life the title character drops, and it takes Russell a little time to realize that Rusty, as the child is known, is himself when he was eight years old. It takes him a bit longer to understand that Rusty--whom he at first believes to be a hallucination--is the means by which he can begin to understand why he has, at age 40, become such a cold and driven creep, the Scrooge of sterility.
As Rusty scornfully discovers, he doesn't even have a dog. Or the highly developed taste for junk food he once enjoyed. Eventually the kid conducts Russell back to his past to find out what ails him, what makes him so angry with the world.
What he learns is not exactly earth-shattering. But perhaps the ordinariness of his troubles is one of the movie's points. It doesn't take much to turn a life sour. It can take quite a bit of effort to sweeten it after the bad, vengeful habits have set in. What's good about this movie, written with witty restraint by Audrey Wells, is that it doesn't try to explain how Rusty arrived in the year 2000 from 1968. He is not an angel from heaven; he's just a kid lost in a time warp, as puzzled as anybody else about the trip he's on, and often hungry. Nor does the director, Jon Turteltaub, make a big mawkish deal out of this strange voyage of discovery. It just unfolds, making no particular effort to loosen our tear ducts.
It's nicely played too--particularly by Willis, who neatly nails both his character's funny nastiness and his unsentimental reform once he begins to recover from his emotional amnesia. One doesn't want to oversell The Kid. It's a modest little fantasy. But it's also well made, unpretentious and refreshing--like a cool and fizzy bottle of soda pop on a hot summer's day.