Though shameless enough at plunking the old heartstrings until they all but beg for mercy, "To Find My Son," tonight's CBS movie at 9 on Channel 9, makes for a fairly presentable story about beating the pants off city hall.

Richard Thomas, misty-eyed as ever and looking prematurely seedy (and suggesting, with a newly acquired mustache, a young Laurence Harvey, of all unfortunate things), plays a 23-year-old bachelor who wants to adopt a 7-year-old boy but is blocked by rules and regulations and the heartless drones who enforce them. He and the kid have taken a real shine to each other, but this means nothing to the cold, unfeeling bureaucrats who man "The Downtown Office" of the child welfare authority.

"Inspired by a true story" -- in other words, liberally fudged -- the script by Sandor Stern hovers like a curious bee over the psychological truth at the heart of the matter: Parents aren't the only ones who experience parental feelings. But Stern and director Delbert Mann, astute practitioners of emotional manipulation, prefer mush to theme. And so, there are lots and lots of shots of Thomas and the kid (Justin Dana) just having a wonderful time and indulging in oodles of Hollywood Hugs, as Captain Airwave calls them.

The Whole World seems to be against this relationship made in heaven, but the most formidable opposition comes from Allyn Ann McLerie, masterful and commanding, to put it mildly, as Mrs. Braggs, whose 23 years in the downtown office have made her unyielding and doctrinaire with a vengeance.

Perhaps to the writer's and director's credit, there are times when one doubts whether the seemingly inevitable happy ending really will materialize in the knick of time -- i.e., about 10:56 p.m. Also to everyone's credit is a scene in a toy store when boyfriend and girlfriend who've called it splits share one of those exquisitely awkward polite hellos. If more of "To Find My Son" had been this observant and subtle, it could have coaxed a few tears rather than just jerking them.