Poor direction and a mediocre script sabotage what might have been an inspirational sure thing in "Nobody's Child," the CBS Sunday night movie at 9 on Channel 9. Marlo Thomas, whom one is naturally inclined to root for, gets to do nearly as much suffering in the first 20 minutes of this film as Jessica Lange did in any given 40 of "Frances."

But the viewer suffers, too, from what might be considered flashback whiplash, trying to piece things together from the clumsy clues tossed by writers Mary Gallagher and Ara Watson and so-so director Lee Grant. Instead of relating this "based on a true story" case with simplicity and clarity, the filmmakers opt for artsy touches that, in a TV movie, are merely befuddling.

Thomas plays Marie Balter, who not only survived 20 years in a Massachusetts mental institution, but emerged into the daylight and a life of self-reliance and productivity. How she got into a state of extreme emotional anxiety is not very cogently explained in the film, and even an adept director would have had trouble juggling the prefatory shock-cut flashbacks that elude the control of the slippery-fingered Grant.

These flashbacks go on for so much of the film and in such sloppy profusion that "Nobody's Child" begins to look like the movie that will never really get started.

Since the film was photographed by Sven Nykvist, no less, it looks pretty good, but awkward disorganization discourages much empathy with the main character and her plight. Thomas is solid and sure-footed in the role, though, and even if the film contains too many tour-de-forcey "mad" scenes and actress exercises, she does create real life from the muddled script and despite Grant's ice-cold direction.

The story begins in 1964 when Balter is diagnosed as "severely depressed" and disoriented. There are lots of "Snake Pit" scenes of mental patients acting deranged, none of it very convincing, and then the story jumps to 1965, where it is declared without much explanation that Balter, by now 36, has made a miraculous recovery.

In time she will leave the institution for a governess job with a sympathetic family, attend college, take the bold step of renting her own apartment, get married to an affable manic-depressive (so very nicely played by Ray Baker) and face one last, and in a TV movie inevitable, emotional crisis.

We are cheered to see her overcome her obstacles, but if the film had been told with more wit and more coherence, it might have shed some light on the pervasive problem of depression, and it could have made Balter's victory triumphant, not just doggedly prosaic. Also, the film tends to foster the impression that the deinstitutionalization of mental patients is ipso facto a good idea, when in fact it has proven otherwise in many, many cases.

Repeatedly, Balter's sudden recovery is attributed to the fact that she is "stabilized on her medication." The medication is not named. If it were, we would probably all be stampeding doctors' offices on Monday morning demanding a prescription.

'Fathers and Sons'

NBC premieres another squeaky-dull kiddie-targeted sitcom, "Fathers and Sons," Sunday night at 7 on Channel 4. It stars Merlin Olsen, America's oldest flower child, as a father and husband and elementary school coach. The preachy lesson of the first show is that pluck and determination can take you a long way. Yes, well. The farther from "Fathers and Sons," the better.