Up to Specs: Martian Child?s father-son bond has shades of weirdness.

Get over the kid’s voice. That’s one key to enjoying Martian Child, an apparent glucose-spiker about a misfit kid and the neurotic widower who adopts him. Like Wristcutters, the film has literary origins, though the screenwriters made a rather significant change: The source novel’s author, David Gerrold, and its main character are single gay men. But widowers are cuddlier, I guess, and don’t risk offending ticketbuyers. A grieving man opening his heart to a child? Aww. A gay man wanting to become a parent? Not in my multiplex.

As it stands, however, Martian Child manages to be rather touching. John Cusack, the most adorable of neurotics, plays David, a science-fiction writer who began the adoption process before his wife’s death. Two years later, the agency has a boy for him, but David’s misgivings about whether he can handle a child by himself are compounded when he meets Dennis (Bobby Coleman). Dennis thinks he’s from Mars, and since that planet is much farther from the sun than Earth, he spends his time in a box—from Amazon, marked fragile, no less—to protect himself from solar rays. Dennis also wears a weight belt, lest he float right back into space. David also used to pretend he was an alien when he was a kid, so naturally, he’s compelled to reach out to Dennis and try to get him, literally, out of his shell.

The setup’s a little obvious, and director Menno Meyjes doesn’t do his film any favors by having Dennis speak in a grating cracked whisper—just in case you missed the rest of the reminders of his otherness, such as his sunscreen-slathered, Marilyn Manson complexion, weird haircut, and enthusiasm for taking Polaroids to document his “mission.” There’s also a nonsensical conflict that involves the adoption agency threatening to take Dennis out of David’s well-appointed home just because Dad isn’t turning to therapists and Ritalin for help.

But the things Martian Child gets right are strong enough to save it. The humor comes courtesy of the typical Cusack sarcasm. John’s is slightly toned down (though he’s still far from Must Love Dogs territory). His sister, Joan, stars as David’s sister, Liz, who as a mother gives him insights such as, “The thing about kids is that they keep coming at you. Like mosquitoes.” The story’s central idea, however overplayed, is the gut-grabber, though. Only former cheerleaders and quarterbacks won’t bristle when another girl calls Dennis a “weirdo.” But while David’s sympathy for Dennis’ social issues and fondness of his offbeat personality is obviously warming—even Amanda Peet, as David’s sorta love interest, supplies a nice moment when her character marvels that Dennis “is like a little Andy Warhol”—he also eases him into the idea that sometimes fitting in is OK, too. Consider these relatively surprising doses of reality the film’s own weight belt.