In one TV movie this week the law is an obstacle in the search for a missing youth. In another, it is triumphant in its effort to resolve an uncommonly brutal cop-killing. And in a third, the law is the common enemy of two men who otherwise have nothing in common at all.

CBS offers "Into Thin Air" (Tuesday at 9) based on the true story of a youth's disappearance in 1978. Ellen Burstyn stars as the Ottawa mother who sees her son (Tate Donovan) off to summer school in Boulder, Colo. -- in a delightful send-off scene reminiscent of "Risky Business" -- only to become progressively more disturbed when he never calls back after reporting problems with his van in Nebraska.

The 19-year-old's mother and brother, played by Sam Robards (Lauren Bacall and Jason's son), do much of their own missing- persons work in the face of a general breakdown in police cooperation and hopeless tangles of red tape in which there has as yet been no crime or accident.

"It's a continuing problem in this country," said Joe Stern, the show's producer. "There are 750,000 disappearances each year . . . One of the problems is that law enforcement is not set up to take care of such cases. This film deals with the problems of missing 18-, 19- and 20-year-olds, not the younger ones you see on milk cartons."

Burstyn, a mother of three children, said in an interview that if she were faced with such a problem, she would hire a private detective to find her child.

That's what her character does in "Into Thin Air." Robert Prosky is the private eye, a retired cop who laments the loss of pride in police work. His persistence -- he drags his wife across Utah to run down leads over Thanksgiving -- stands in sharp reliefagainst the computer-equipped police and FBI, who simply let the case drag.

Burstyn recalled that after she finished the film, one of her children, a rock musician, stuffed his equipment in a van and headed cross-country. "The last words I said to him were, 'Don't pick up any hitchhikers.' " They had agreed that he would phone home each night. "Okay," he said to his upset mother after missing a call one night, "I guarantee every other night."

"Badge of the Assassin" (Saturday at 9 on CBS), based on the book by Robert K. Tanenbaum and Philip Rosenberg, deals with the pursuit of the killers of two New York policemen in the early '70s, a search that spanned the country and included contributions from several police forces.

"I wrote the book to illustrate the time, commitment and cooperation necessary to make the criminal justice system work," said Tanenbaum, who was the assistant district attorney who headed the search for the killers. Later he served as deputy chief counsel in charge of the probe by the House Select Committee on Assassinations of the John F. Kennedy killing. Tanenbaum, who is now in private practice in California, was also executive producer for this movie. He is played in the film by James Woods.

Yaphet Kotto costars as Cliff Fenton, a resourceful, street-wise New York policeman who was a key figure in unraveling the case. Later, Fenton was named the House committee's chief Kennedy assassination investigator, and is now assistant regional inspector general for investigations for the U.S. Department of Health and Human Services.

"I pulled out all the acting stops I could," said the very straightforward Kotto. "After this, people will never look at a black actor the same way again."

They may soon look at him in a very new way. He's cast in a romantic role opposite a blonde woman in an episode of "Alfred Hitchcock Presents." "I couldn't believe it as I read the script," recalled Kotto. "I thought, 'They're getting closer and closer.' It must mean my character is going to die . . . Then they were hugging and kissing . . . I called the studio and said, 'There must be mistake. This is Yaphet Kotto, not Billy Dee Williams.' "

Tonight at 9 on ABC, unless the World Series goes a seventh game, Robert Urich and Carl Weathers team up in a remake of "The Defiant Ones," a 1958 movie starring Sidney Poitier and Tony Curtis.

Weathers, who co-produced the remake with Urich, said the original film was a large part of his inspiration to become an actor. "I was a young boy when I saw it," said Weathers, now 37. "It was an event at the time. I remember standing in line in New Orleans to see it at a time of segregation. There was this incredible statement made -- we are all chained together and unless we find a way to work together, we will be dragged down together."

The film deals with an interracial pair of convicts who escape from a prison manacled together. "They are two men who have differences, but don't understand what those differences are, how they are rooted -- but who transcend those differences when they face a common enemy, the law."

Urich and Weathers formed their own personal and professional bond while developing the show for television. Weathers said that Urich wanted him to play Hawk in his "Spenser: For Hire" series, but that he had to decline. Avery Brooks, who got the part, is grateful.

Note: If the World Series goes to seven games, the show will be rescheduled.