“NOBODY’S CHILD,” Sunday, 9-11 p.m. (2) (8)...

“NOBODY’S CHILD,” Sunday, 9-11 p.m. (2) (8) (Illustrated on the cover)--Triumph-over-adversity stories are usually routine TV, the always reliable tears building to thunder, followed by a heart-thumping crescendo of cymbals.

This one is special, though, thanks largely to director Lee Grant and also to Marlo Thomas (shown on the cover). Thomas is splendid in a two-hour CBS story about the real-life Marie Balter, who spent nearly 20 years in a mental institution. She went on to get a master’s degree from Harvard and work as a supervisor in a mental health agency.

We first meet Marie when she is a suicidal, emotionally disturbed adult living in an institution, unable to distinguish between the present and images of her tortured past. She suffers from paranoia and hallucinations.

Most everyone gives up on Marie. However, encouraged by a nurse, a doctor (“I look into Marie’s eyes and I see someone there”) and a few others, Marie begins to make slow improvement and the dominoes begin to fall.

She ultimately progresses to where she can live with a family outside the institution, work in an office and attend college.

Nothing is rushed in the script by Mary Gallagher and Ara Watson, though. Marie makes fitful progress and many of her demons linger, even after her courtship by a manic depressive (Ray Baker), whom she will ultimately marry. Their tenuous wedding night is a sweet scene, tenderly shaped by Grant.

Even more memorable, though, is a later sequence in which Marie the adult and Marie the child embrace in a sort of symbolic completion representing Marie’s ultimate reconciliation with her traumatic childhood. It’s just beautifully done.

There remains a sense of mystery about Marie Balter. You sense there are doors left unopened in “Nobody’s Child,” but not by Thomas, who is somehow luminous in an unglamorous role. It’s a fine job of acting, heartfelt and true, short on cheap sentiment, long on honesty.