David didn’t father this child, though, so the shared tendency for fantasy is not down to genetics. He adopted Dennis, and gravitated toward the kid because, well, he was a bit of a weirdo as a child, too, and sees not only a bit of himself in Dennis but also an opportunity to use his understanding of the power of the imagination to help a kid on the verge of being written off as hopeless.

Ah, but that sounds hopelessly sentimental, yet none of it plays out that way in Martian Child, for all that the potential for drowning the audience in melodrama was there. There are signs, early on, that we could have been heading for some terribly clichéd complications: Amanda Peet (Syriana, The Whole Ten Yards) as the sister of David’s dead wife presents romantic options for alleviating David’s crushing loneliness, but the sudden new attraction between them never overwhelms the larger story, and remains a tantalizing path for imagining the story continuing on long after the movie ends. The “dramatic” courtroom battle that seems to be threatening -- as David struggles with Dennis’s many problems even as he grows to adore the kid, and social services is reconsidering their decision to let a single man adopt -- never develops.

Which is all as it should be. This is, wonderfully, a smart and snappy -- never sappy -- portrait of a budding parent-and-kid romance, and a lovely ode to nonconformity, to being your own person even if the rest of the world has some issues with that. And the deeply satisfying ordinary magic and everyday mystery of seeing two unlikely people come together and make a life for themselves is not all down to Cusack’s everyguy charisma, though that might have been enough -- certainly, Cusack (1408, The Ice Harvest) can make a line such as “You’re just a freaky little dude, man,” directed at Dennis, sound like a valentine, an expression of loving approval. But Bobby Coleman (Must Love Dogs), as the prickly Dennis, is able -- astonishingly, for an actor of such tender years -- to create a Dennis who is both difficult to like and impossible not to love. I’d never imagined a child actor could project both “inscrutable” and “vulnerable” in quite such a winning combination, but Coleman is fascinating to watch as his Dennis slow unfurls himself to the possibility that here, in David, is finally a parent who is not going to abandon him.

Based on a semiautobiographical novel by science fiction writer David Gerrold (best known for writing what is probably the most popular Star Trek episode ever, “The Trouble With Tribbles”), himself the single father of an adopted son, Martian Child is, in fact, a perfectly apt exploration of love and family in the early 21st century, seen through the cynical-but-melting-toward-tenderness Generation X gaze. As pop culture’s embracing of science fiction and everyone’s embracing of modern science-fictional technology has shaped us, it seems impossible not to funnel ideas about love and family through a lens that encompasses the vastness of the universe and the smallness of ourselves within it. Maybe only a Gen X icon like Cusack could have sold us on that at this very moment... and he does.

(Technorati tags: Martian Child, John Cusack, David Gerrold)