‘Unsolved Mysteries’: Cracking Cases and Repairing Lives : Television: NBC series mixes theater with public service in solving 35 crimes and reuniting 10 pairs of loved ones.

But for its modern, mass-media twist, the story is right out of Dickens.

Their mother dead of cancer, three children cling fiercely to each other in the temporary care of a family friend. A year goes by, and finally word comes from the court: The oldest is to be shipped off to Texas to live with the troubled father who left the family years before. The younger two are adopted into a settled, middle-class life with a childless couple in Maine.

There in Texas, LeeAnn Robinson chafes under life with a difficult father and longs for her brother and sister. She runs away at 16 and vows to find them. She eventually succeeds.

But here’s the twist. Robinson, who now lives in Westchester and makes her living selling Mary Kay Cosmetics, found her family through television. She searched them out through an appearance on the NBC program “Unsolved Mysteries.”

“I was standing there in the studio (after the program ran) and this guy came over and said, ‘I have your sister on the phone,’ ” Robinson said in an interview. “I just started to cry. I cried for a week.”

Robinson’s reunion with sister Tami Bouchard and brother Jim Chapman was shown on Wednesday’s regular broadcast of “Unsolved Mysteries.” And their story will be featured again in “Unsolved Mysteries Third Anniversary Special Edition,” which preempts “My Two Dads” and “Sister Kate” at 8 p.m. Sunday.

Produced by Terry Dunn Meurer and John Cosgrove, “Unsolved Mysteries” boasts of solving 35 crimes, finding two missing heirs and reuniting 10 sets of loved ones. Hosted by actor Robert Stack, it is among the most popular programs on TV this season, finishing 10th last week.

“Unsolved Mysteries” grew out of a series of three specials produced by Cosgrove and Meurer for NBC in 1986, called “Missing . . . Have You Seen This Person?” They broadened the concept and introduced “Unsolved Mysteries” on Jan. 20, 1987, first as a succession of specials, then as a weekly series in the fall of 1988.

Like some newspaper tabloids, “Unsolved Mysteries” has a formula: “Almost every show has an unexplained death in it, and almost every show has a lost love story,” Meurer said. “Then we’ll mix and match in there a legend or a gold mine, or we’ll put in one of our UFO stories.”

For viewers, such “reality” shows provide a voyeuristic satisfaction similar to that offered by once-popular programs such as “This is Your Life” and “Candid Camera.”

“Unsolved Mysteries” adds to that stew an element of interactivity--now the viewer is the sleuth, watching the show for photographs or other clues that may lead to a discovery that a next-door neighbor is a criminal or a long-lost heiress.

“People are fascinated by the idea that they might be living next door to one of these people, and might be able to help find them,” said producer Meurer.

And while some of the reality programs have been criticized as prurient and exploitative, those behind “Unsolved Mysteries” say they’re doing a service for people. They say Sunday’s anniversary show--with its focus on the repaired lives and newly closed cases that have resulted from earlier programs--is the proof.

“The basic question, and we’ve all thought about it, is, ‘Is it an intrusion into somebody’s life?’ ” Stack said. “But all the people we’ve helped on the show have been very happy to have their mysteries solved.”

In most cases, a spot on “Unsolved Mysteries” comes as a result of a plea from a person who is looking desperately for someone, and approaches the show as a last resort, Muerer said.

Hungarian immigrant Carl Dentai, for example, went on the show after more than 40 futile years in search of the American soldier who had befriended him and his family just after World War II.

It was Christmastime, and Dentai and his family were living in a freight car on the outskirts of Linz, Austria. A knock on the car’s big iron door produced Signal Corpsman Phillippe Pelletier, fresh from a British hospital and with an invitation to a holiday party the soldiers were throwing for the children of the refugees.

Pelletier befriended the family, coming often to the cramped train yard to play chess. But after Pelletier was transferred back home, the two men lost track of each other.

“For 40 years I can’t find him and then the show finds him in 40 minutes,” said Dentai, who brought his family to the United States after the war and settled in Michigan.

“I was looking for him in newspaper ads since 1956. Then I saw the ‘Unsolved Mysteries’ show and sent a letter to NBC in New York.”

But to say that the program relies solely on fate to find its subject matter may be a little disingenuous.

“ ‘Unsolved Mysteries’ advertised in the veterans newspaper, saying the show wanted soldiers who were looking for nurses who treated them in Vietnam,” said vet James Meade, who was reunited with nurse Karen Nelson after an appearance on the program. “The ad said the person who wrote the best letter would get on the show.”

Meurer insisted that the incident was not typical. “That’s the only ad we ever put in the paper,” she said. “That was the researcher’s idea.”

But if “Unsolved Mysteries” does produce its subjects as much as simply find them, perhaps that in itself is an analogy of what the show is all about.

“We’re balancing two needs here,” said host Stack. “We’re trying to produce theater and we’re trying to do a public service.”