Based upon an award-winning short story from sci-fi writer David Gerrold, "Martian Child" is loosely based upon Gerrold's own experiences in being a single gay male who adopted a child.

Of course, I say "loosely" based because in "Martian Child," John Cusack plays David Gordon, a recently widowed man who decides to honor the wishes of his late wife by honoring the wishes of his late wife by adopting a child. In this case, David adopts Dennis (Bobby Coleman), a troubled young boy who insists he is from Mars.

Supported by his sister Liz (real-life sister Joan Cusack) and his wife's best friend Harlee (Amanda Peet), David gradually starts to win the young boy's trust even while dealing with professional pressures from his agent (Oliver Platt) and publisher (Anjelica Huston).

Let's be honest. There's few actors who can play the wounded loner/good guy as competently as John Cusack. David Gordon is a role Cusack could do in his sleep, but Cusack stays wide awake and offers a surprisingly affecting and touching performance even when the script's overwhelming schmaltz and sentimentality betrays his performance's natural authenticity.

As David and Dennis grow closer, the lines between fantasy and reality grow thinner as the two begin to grow comfortable in each other's world.

However, much like the similarly themed "K-Pax," "Martian Child" can never seen to decide what it really wants to be. While even the film's website labels the film a "romantic drama," the platonic flirtations between Harlee and David are clearly secondary to the father-son drama that unfolds.

Is David simply stuck in complicated bereavement? Is Dennis a severely abused child escaping to a fantasy world? Is Dennis, perhaps, really from Mars? Can a child this broken really be loved back to life?

By the time "Martian Child" begins to reveal the answers to these questions, director Menno Meyjes (Oscar-nominated screenwriter for "The Color Purple") has so completely poured on the emotion that the easily predicted happy ending almost feels anti-climactic yet still oddly satisfying.

The fact that "Martian Child" survives its emotional histrionics is largely owing to the two leads, Cusack and Coleman, who also appeared in "Must Love Dogs" together. Cusack, who also appeared in Meyjes' penned "Max", is emotionally exuberant as the grieving widow who realizes that adopting a child simply because his wife wanted to "isn't good enough."

While Coleman's quiet and breathy acting style is a bit eerie at times, and more than a little bit reminiscent of the recent horror-thriller "Joshua," Coleman's chemistry with Cusack allows for a wonderful vulnerability between the two that brings the script to life much better than it really should.

Amanda Peet does a nice job as Harlee, though it's hard to deny that the semi-flirtatious relationship feels out of place and awkward given the considerable emotional depth that surrounds it. Joan Cusack shines, as usual, and offers the film much of its humor. Emmy-winner Richard Schiff ("The West Wing") is restrained in what could have easily been a caricaturish bad guy role as a Children's Services worker leery of David's parenting, while Sophie Okonedo ("Hotel Rwanda") adds a nice spark as the group home director who first contacts David about Dennis.

The production design complements the script quite nicely, though much like the Seth Bass/Jonathan Tolins script it occasionally utilizes the sledgehammer approach to get its point across.

Almost despite itself, "Martian Child" rests upon the strength of its ensemble cast and their uniform ability to overcome a schmaltzy script and manipulative direction to create a sweet, heartwarming and life-affirming film.